Curable media for implantable medical device

ABSTRACT

A subcutaneously formed in place orthopedic fixation device is provided, such as for fixation of the spine or other bone or bones. The device comprises an inflatable member, such as a tubular balloon. The balloon is positioned at a treatment site in the body while in a flexible, low crossing profile configuration. The balloon is thereafter inflated with a hardenable epoxy media comprising one or more epoxy compounds and one or more amine curing compounds that cures rapidly in place with low to moderate exotherm. Methods and delivery structures are also disclosed.

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 10/161,554, filed on May 31, 2002, which is a continuation-in-partof U.S. patent application Ser. No. 09/976,459, filed on Oct. 10, 2001,which is a continuation-in-part of U.S. patent application Ser. No.09/943,636, filed on Aug. 29, 2001, which is a continuation-in-part ofU.S. patent application Ser. No. 09/747,066, filed on Dec. 21, 2000,which claims priority to U.S. Provisional Patent Application No.60/213,385, filed Jun. 23, 2000, entitled “Percutaneous Interbody FusionDevice,” the contents of each of which are incorporated in theirentirety into this disclosure by reference

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to medical devices and, moreparticularly, to systems for forming orthopedic fixation orstabilization implants in place within the body, such as by infusing aformable media into a cavity. In one application, the present inventionrelates to minimally invasive procedures and devices for forming aspinal stabilization rod in situ.

[0004] 2. Description of the Related Art

[0005] The human vertebrae and associated connective elements aresubject to a variety of diseases and conditions which cause pain anddisability. Among these diseases and conditions are spondylosis,spondylolisthesis, vertebral instability, spinal stenosis anddegenerated, herniated, or degenerated and herniated intervertebraldiscs. Additionally, the vertebrae and associated connective elementsare subject to injuries, including fractures and torn ligaments andsurgical manipulations, including laminectomies.

[0006] The pain and disability related to these diseases, conditions,injuries and manipulations often result from the displacement of all orpart of a vertebra from the remainder of the vertebral column. A varietyof methods have been developed to restore the displaced vertebrae orportions of displaced vertebrae to their normal position and to fix themwithin the vertebral column. For example, open reduction with screwfixation is one currently used method. The surgical procedure ofattaching two or more parts of a bone with pins, screws, rods and platesrequires an incision into the tissue surrounding the bone and thedrilling of one or more holes through the bone parts to be joined. Dueto the significant variation in bone size, configuration, and loadrequirements, a wide variety of bone fixation devices have beendeveloped in the prior art. In general, the current standard of carerelies upon a variety of metal wires, screws, rods, plates and clamps tostabilize the bone fragments during the healing or fusing process. Thesemethods, however, are associated with a variety of disadvantages, suchas morbidity, high costs, lengthy in-patient hospital stays and the painassociated with open procedures.

[0007] Therefore, devices and methods are needed for repositioning andfixing displaced vertebrae or portions of displaced vertebrae whichcause less pain and potential complications. Preferably, the devices areimplantable through a minimally invasive procedure.

SUMMARY OF THE INVENTION

[0008] In accordance with one embodiment, there is provided a formed inplace orthopedic device. The device comprises an outer wall, defining acavity therein and a hardenable media within the cavity to form theorthopedic device, said hardenable media comprising a resin and hardenermixture that is substantially cured at a temperature below about 45° C.in about 90 minutes or less, wherein the hardenable media is hardenedwhile the device is positioned within the body of a patient to createthe formed in place orthopedic device.

[0009] In accordance with another embodiment, there is provided a bonefixation device. The device comprises a delivery catheter comprising aninflatable member, a hardenable media contained within the inflatablemember, and at least two anchors having portals, wherein the inflatablemember extends through the portals of the anchors. The hardenable mediacomprises an epoxy that cures to a hardened form having a staticcompression bending value (ASTM F1717) of at least 90 lbs in about 90minutes or less.

[0010] In accordance with another embodiment, there is provided anorthopedic fixation device. The device comprises an elongate, flexibletubular body having a distal end and a proximal end, said body forming acentral lumen, a manifold at the proximal end of the tubular bodycomprising at least one port, an inflatable member having a proximalend, a distal end, and an interior, removably attached to the distal endof the tubular body a hardenable media for inflating said inflatablemember, said hardenable media comprising about 45-52% by weight aromaticdiepoxide resin, about 19-23% by weight aliphatic diepoxide resin, about20-29% by weight dialkylamines and about 4-9% cycloalkylamines; and avalve, provided at the proximal end of the inflatable member.

[0011] In accordance with another embodiment, there is provided a methodof forming an orthopedic device at a treatment site within the body of apatient, comprising the steps of positioning an outer wall at thetreatment site within the patient, the outer wall defining a chambertherein, and introducing a hardenable media into the chamber, whereinthe hardenable media cures from a liquid form to a hardened form havinga static compression bending value of at least 90 lbs (ASTM F1717) inabout 90 minutes or less.

[0012] In accordance with another embodiment, there is provided a methodof stabilizing an orthopedic fracture, comprising inserting at least twoanchors having portals into a bone, delivering an orthopedic devicecomprising an inflatable balloon to the bone, and inflating said balloonwith a hardenable media comprising about 45-52% by weight aromaticdiepoxide resin, about 19-23% by weight aliphatic diepoxide resin, about20-29% by weight dialkylamines and about 4-9% cycloalkylamines, whereinsaid orthopedic device extends through said portals, such that saidinflating fixes said anchors in relation to one another.

[0013] In accordance with another embodiment, there is provided a methodof stabilizing an orthopedic fracture, comprising inserting at least twoanchors having portals into a bone, delivering an orthopedic devicecomprising an inflatable balloon through the portals, and inflating saidballoon with a liquid curable material, wherein the inflating step fixessaid anchors in relation to one another and the curable material issubstantially cured at a temperature below about 45° C. in about 90minutes or less. In another embodiment, there is provided a formed inplace medical device, comprising an outer wall, defining a cavitytherein and a hardenable media within the cavity to form the medicaldevice, said hardenable media comprising a resin and hardener mixturethat cures at a temperature below about 45° C. wherein said cured mediahas a static compression bending value (ASTM F1717) of at least 150 lbswherein the hardenable media is hardened while the device is positionedwithin the body of a patient to create the formed in place medicaldevice.

[0014] In preferred embodiments, the hardenable or curable materialcomprises about 45-52% by weight aromatic diepoxide resin, about 19-23%by weight aliphatic diepoxide resin, about 20-29% by weightdialkylamines and about 4-9% cycloalkylamines. In an especiallypreferred embodiment, the aromatic diepoxide resin comprises diglycidylether of Bisphenol A or diglycidyl ether of Bisphenol F; the aliphaticdiepoxide resin comprises one or more alkane diols of glycidyl ether;the cycloalkylamines are N-aminoalkylpiperazines; and the dialkylaminesare according to the formula H₂N—R—NH₂, wherein R is a branched orunbranched C₂-C₁₀ alkyl group. The hardenable media, when substantiallycured, preferably has a static compression bending value (ASTM F1717) ofat least about 60 lbs, and at least about 100 lbs when fully cured. Themedia is preferably substantially cured in about 90 minutes or less, andthe curing takes place at a temperature of about 45° C. or less, morepreferably about 43° C. or less.

[0015] Further features and advantages of the present invention willbecome apparent to those of skill in the art in view of the detaileddescription of preferred embodiments which follows, when consideredtogether with the attached claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a side elevational view of a delivery catheter having aninflatable fixation device thereon.

[0017]FIG. 2 is a cross-sectional view taken along the line 2-2 of thedelivery catheter of FIG. 1.

[0018]FIG. 3 is a side elevational cross section of a proximal portionof the delivery catheter of FIG. 1.

[0019]FIG. 4A is a side elevational cross section of a distal portion ofthe delivery catheter of FIG. 1.

[0020]FIG. 4B is a detailed view of the inflatable fixation device ofFIG. 4A.

[0021]FIG. 4C schematically illustrates a cross-section through acomposite formable rod in accordance with one aspect of the presentinvention.

[0022]FIG. 5 is a side elevational view of the inflatable fixationdevice of FIG. 1.

[0023]FIG. 6 is a cross-sectional view through the inflatable fixationdevice of FIG. 5, in the expanded position.

[0024]FIG. 7A is a schematic cross-sectional view of a valve of theinflatable fixation device of FIG. 6.

[0025]FIG. 7B is a schematic cross-sectional view of an alternate valve.

[0026]FIG. 7C is an end view of the valve of FIG. 7B.

[0027]FIG. 8 is a perspective view of the manifold of the deliverycatheter of FIG. 1.

[0028]FIG. 9 is a side elevational view of a portion of the spine,having a formable orthopedic fixation system implanted therein.

[0029]FIG. 10 is a side elevational view of a bone anchor.

[0030]FIG. 11 is a side elevational view of the bone anchor of FIG. 10,rotated 90° about its longitudinal axis.

[0031]FIG. 12 is a longitudinal cross-sectional view of the bone anchorof FIG. 11.

[0032]FIG. 13 is a side elevational view of an alternative embodiment ofa bone anchor, with bone ingrowth apertures.

[0033]FIG. 14 is a side elevational view of a screwdriver.

[0034]FIG. 15 is a side elevational view of an alternative embodiment ofa screwdriver.

[0035]FIG. 16 is a side elevational view of a guidewire directingdevice.

[0036]FIG. 17 is a top plan view of a directing sheath.

[0037] FIGS. 18-28 are partial cross-sectional midline sagittal views ofa portion of a vertebral column showing an implantation method of thepresent invention.

[0038]FIG. 29 is a posterior elevational view of a portion of avertebral column post-procedure, with two fixation devices mountedthereon.

[0039] FIGS. 30-32 are posterior elevational views of a portion of avertebral column showing a method of the present invention using adirecting sheath.

[0040]FIG. 33 is a side elevational view of a cross tie held in positionby a cross tie deployment system, in-between a first and a secondpedicle screw.

[0041]FIG. 34 is a side elevational view as in FIG. 33, illustrating aninflatable connection rod inflated between the first and second pediclescrews, with a cross tie mounted thereon.

[0042]FIG. 35 is a posterior elevational view of a portion of avertebral column, post procedure, with two inflatable connection rodsand one crossbar mounted thereon.

[0043]FIG. 36 is a perspective, schematic view of various components ofthe cross tie system.

[0044]FIG. 37 is a perspective view of a cross tie.

[0045]FIG. 38 is a side elevational view of a portion of a spine, havingan alternate crossbar connected to an inflatable connection rod.

[0046]FIG. 39 is a posterior elevational view of a portion of avertebral column, showing the crossbar of FIG. 38.

[0047]FIG. 40 is a side elevational perspective view of a tubularcrossbar sheath.

[0048]FIG. 41 is a side elevational schematic view of the crossbarsheath of FIG. 40, mounted on a deployment catheter.

[0049]FIG. 42 is a schematic perspective view of the crossbar deploymentsystem of FIG. 41, positioned within two pairs of opposing pediclescrews.

[0050]FIG. 43 is a partial cutaway side elevational view of a sheath asin FIG. 40, having an inflatable balloon positioned therein.

[0051]FIG. 44 is a schematic side elevational view of the distal end ofdeployment catheter having a heated implant removably positionedthereon.

[0052]FIG. 45 is a schematic side elevational view of an implant havingan alternate heating element.

[0053]FIG. 46 is a frontal view of the control panel for the heatingelement.

[0054]FIG. 47 is a block diagram of a driver circuit for driving aheating element in accordance with the present invention.

[0055]FIG. 48A is a side elevational view of an alternate implant inaccordance with the present invention, having a resistance heating coilpositioned therein.

[0056]FIG. 48B is an enlarged fragmentary view of the proximal end ofthe implant illustrated in FIG. 48A.

[0057]FIG. 48C is an end view taken along the line 48C-48C of FIG. 48B.

[0058]FIG. 49 is a side elevational schematic view of the distal end ofa deployment catheter in accordance with the present invention, with theimplant removed.

[0059]FIG. 50 is a side elevational schematic view of the proximal endof the deployment catheter illustrated in FIG. 49.

[0060]FIG. 51 is a side elevational view of the removable junctionbetween the distal end of the deployment catheter and the proximal endof the implant.

[0061]FIG. 52 is a side elevational view of a stiffening wire inaccordance with one aspect of the invention.

[0062]FIG. 53 is a graph showing time versus temperature duringpolymerization of a hardenable rod formed in situ.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0063] Although the application of the present invention will bedisclosed primarily in connection with a spinal fixation procedure, themethods and devices disclosed herein are intended for use in any of awide variety of medical applications where formation of an attachment,bulking, support, fixation or other element in situ may be desirable.

[0064] One advantage of the in situ prosthesis formation in accordancewith the present invention is the ability to obtain access to atreatment site through a minimally invasive access pathway, whileenabling the formation of a relatively larger implant at the treatmentsite. This allows procedure morbidity to be minimized, since opensurgical cutdowns or other invasive access procedures may be avoided. Inaddition, the in situ formation in accordance with the present inventionallows the formation of an implant having any of a wide variety ofcustomized or predetermined shapes, due to the ability of the infusiblehardenable media to assume the shape of the cavity or flexible containerinto which it is infused.

[0065] The methods and devices of the present invention additionallyenable access to a treatment site within the body along a curved andeven tortuous pathway, through which a preformed prosthesis would notfit or would not be navigable. The detachable inflatable prosthesis ofthe present invention, removably coupled to the distal end of anelongate flexible tubular catheter body, can be dimensioned forpercutaneous, surgical or transluminal advancement and deployment of aninflatable or otherwise curable in place prosthesis in any of a widevariety of orthopedic applications, such as the spine as disclosed ingreater detail below, as well as long bones, short bones, and associatedligaments and tendons. In addition, the deployment catheter andprosthesis can be dimensioned for transluminal navigation throughout thecardiovascular system, the gastrointestinal tract, the biliary tract,the genitourinary tract, or the respiratory tract (e.g. thetracheobronchial tree). The device may thus be advanced throughartificial access pathways as well as naturally occurring lumens andhollow organs. Additional applications of the in situ device formationtechnology of the present invention will become apparent to those ofskill in the art in view of the disclosure herein.

[0066] In connection with spinal fixation applications, the presentinvention involves inserting one or two or more bone anchors having aconnector such as a portal into at least a first and a second adjacentor nonadjacent vertebra. An implantable, inflatable orthopedic device isinserted through the portals and inflated to lock to the bone anchorsand stabilize the bone components. A deployment system, comprising adelivery catheter removably carrying the implantable device, isprovided, such that the procedure may be conducted in a percutaneous orminimally invasive manner to minimize procedure trauma to the patient.

[0067] The deployment system shown in FIG. 1 comprises a deliverycatheter 100 which deploys the implantable inflatable orthopedic device102. Delivery catheter 100 preferably includes an elongate, flexibletubular body 104, having a proximal end 106 and a distal end 108. Forcertain applications, however, in which direct linear access isintended, the tubular body 104 may be substantially rigid. The tubularbody 104 includes one or more passages or lumens extending axiallythrough the body, depending upon the desired functionality of thedevice.

[0068] The overall length and cross sectional dimensions of the deliverycatheter 100 may be varied, depending upon the intended clinicalapplication. In a device intended for percutaneous or minimally invasivefusion of lumbar and/or sacral vertebrae, for example, the tubular body104 will generally have a length within the range of from about 15 cm toabout 50 cm, and a diameter within the range of from about 2 mm to about6 mm.

[0069] Percutaneous insertion of the delivery catheter 100 may befacilitated by the provision of a removable elongate stiffening wire122, extending through a lumen such as inflation lumen 130 (see FIG. 2)from the proximal end 106 of tubular body 104, to the distal end 108 oftubular body 104. Optionally, the stiffening wire 122 extends into, andeven all the way to the distal end 118 of the orthopedic device 102, toprovide support and column strength to the device 102 which may bedesirable during tissue penetration. The distal end of the stiffeningwire 122 may be connected to a coil approximately 8 cm in length toallow for a degree of flexibility.

[0070]FIG. 2 shows a cross-sectional view through the elongate body 104,showing (not to scale) an inner sleeve 110 and an outer sleeve 112. Theinner sleeve 110 defines a first, inflation lumen 130, while a second,venting lumen 132 is defined by the annular space between the innersleeve 110 and outer sleeve 112. The inflation lumen 130 is adapted toreceive the elongate stiffening wire 122 in a sliding fashion through aproximal opening 127 on inner sleeve 110, which in turn extends axiallyinto the outer sleeve 112 by way of port 126 in catheter manifold 124.Although the illustrated embodiment has a dual lumen, concentric orcoaxial configuration, three or more lumen may alternatively beprovided, depending upon the desired capabilities of the catheter. Asingle lumen catheter may also be provided, to accommodate a removablestiffening wire, if utilized, and to facilitate inflation of theimplantable device. Alternatively, a two or more lumen catheter shaftmay be fabricated, extruded or otherwise formed with the lumen in aside-by-side configuration.

[0071] The deployment device 100 further comprises a manifold 124,located at the proximal end 106 of the elongate tubular body 104. Thecatheter manifold 124 provides a maneuvering handle for the health careprofessional, and supports an inflation port 126 and a vent port 128.Either or both the inflation port 126 or the vent port 128 may beprovided with a coupling, such as a luer-lock fitting for connection toassociated devices as is known in the art. For example, a luer or otherconnector on the inflation port 126 facilitates connection to a sourceof pressurized inflation media in a conventional manner. The vent port128 may be connected to a syringe or other device to draw a vacuum, toevacuate air from the balloon prior to infusion of the hardenable media.

[0072] The manifold 124 may also include an injection port for allowinginjection of radiopaque contrast fluid to enable visualization of thedelivery device on a fluoroscope. The proximal manifold 124 may bemachined or injection molded of any of a variety of known suitablematerials such as PTFE, ABS, nylon, polyethylene, polycarbonate, orothers known in the art. A precision gasket may also be provided, whichseals securely around the inner sleeve 110, prohibiting fluid loss.

[0073] Catheter manufacturing techniques are generally known in the art,including extrusion and coextrusion, coating, adhesives, and molding.The catheter of the present invention is preferably made in aconventional manner. The elongate shaft of the catheter may be extruded,using polymers such as Nylon, PEBAX, PEEK, PTFE, PE or others known inthe catheter arts, the stiffness of which may be selected asappropriate. Material selection varies based on the desiredcharacteristics. The joints are preferably bonded. Biocompatibleadhesives or heat bonding may be used to bond the joints. The balloonand stent are also made in a conventional manner or in any suitablemanner.

[0074] The deployment system 100 further comprises an implantableinflatable orthopedic device 102, which may function, in a spinal fusionapplication, as an inflatable or formed in place fixation plate or rod.Implantable device 102 is removably carried by the distal end of thetubular body 104, such that inflation lumen 130 is in communication withthe interior cavity 146 of the inflatable device 102. The inflationmedia may thus be infused through inflation port 126 (or opening 127)located at manifold 124 to fill the cavity 146.

[0075] The implantable device 102, which may be a balloon 114, includesa proximal end 116, a distal end 118, and a flexible wall 148. Theballoon 114 may be formed from any of a variety of polymeric materialswhich are known in the balloon angioplasty arts. These include, forexample, complaint materials such as polyethylene, polyethylene blendsor nylon, and substantially noncompliant materials such as polyethyleneterephthalate. Any of a wide variety of other biocompatible polymers maybe utilized, as will be apparent to those of skill in the art in view ofthe disclosure herein.

[0076] The balloon 114 may comprise a single or multiple layers,depending upon the desired physical properties. In one embodiment, theballoon comprises two layers, having a reinforcing structure such as astent or a plurality of axially extending support strips sandwichedtherebetween. In an alternate embodiment, the balloon 114 comprises afirst, inner layer which restrains the hardenable media. A second, outerlayer is coaxially disposed about the first layer, and is provided witha plurality of apertures or a microporous structure. An infusion lumenis provided in the elongate tubular body, for providing communicationbetween a proximal infusion port and the space in between the inner andouter balloon layers. In this manner, fluids, which may contain any of avariety of medications, can be infused into the tissue surrounding thetreatment site. Suitable structures and manufacturing considerations aredisclosed in U.S. Pat. No. 5,295,962 to Crocker et al., the disclosureof which is incorporated in its entirety herein by reference.

[0077] Although a cylindrical configuration for balloon 114 isillustrated herein, any of a variety of alternative cross sectionalconfigurations may be utilized. The overall length, diameter and wallthickness of the implantable inflatable orthopedic device 102 may bevaried, depending on the particular treatment and access site. In oneembodiment, device 102 has an inflated length between about 2 and 12 cm,and often between about 5 cm and about 8 cm for adjacent vertebraefixation. The device 102 has an inflated diameter of generally betweenabout 0.5 and 2 cm.

[0078] The length of the balloon 114 is based upon the anticipateddistance between the first and second anchors, or, in an embodimenthaving more than two anchors, between the anchors having the greatestaxial separation. For example, in a fusion application in which twoadjacent lumbar vertebrae (e.g. L4-L5) are to be fused in an adult, thefirst and second anchors will generally be spaced apart by a distancewithin the range of from about 5 cm to about 8 cm. Preferably, the axiallength of the balloon 114 is sufficiently longer than the inter anchorspacing to permit a portion of the balloon to expand on the “far” sideof the anchor aperture as is illustrated, for example, in FIG. 9. Thus,balloon lengths for the above identified inter anchor distances willgenerally exceed the sum of the inter anchor distance and the anchordiameters by at least about 0.5 cm. Preferably, the balloon extends atleast about 1 cm beyond the portals.

[0079] For use in an application where a first vertebrae is attached toa second vertebrae, and the second vertebrae is separated from the firstvertebrae by at least a third vertebrae, for example in the lumbarspine, the inter anchor distance will generally be within the range offrom about 10 cm to about 20 cm. As will be appreciated by those ofskill in the art, in a three or more vertebrae fixation, theintermediate vertebra or vertebrae will normally but need notnecessarily be connected to the inflatable balloon 114. Thus, in oneapplication, the balloon 114 connects a first attachment point at afirst bone and a second attachment point at a second bone, with one ormore intermediate bones unconnected to the balloon 114. In anotherapplication, at least a third anchor is provided in between the firstand second anchors, and the balloon 114 is threaded through an apertureon each of the first, second and third anchors. The desirability ofattaching or leaving unattached intervening vertebrae or other bones orstructures between two attachment points is a matter of clinicaljudgement, in view of the particular circumstances of the patient.

[0080] The primary function of the balloon 114 is to influence orcontrol the shape of the hardenable media, following injection therein.The implantable balloon 114 is not normally required to restrainpressure over an extended period of time. Thus, a greater designflexibility may be permitted, compared to conventional angioplasty orother dilatation balloons. For example, the balloon 114 may be porous,either for drug delivery as has been discussed, or to permitosteoincorporation and/or soft tissue ingrowth.

[0081] Certain hardenable media which may be utilized in connection withthe present invention, such as PMMA, have a significantly greaterviscosity in the precured form, compared to conventional angioplastyballoon inflation media. In addition, since the balloon 114 is notintended to contain significant pressure, conventional high strengthmaterials such as for high pressure angioplasty may not be necessary.This allows the balloon 114 to be constructed in any of a variety ofways, including techniques utilized for balloon angioplastyapplications. In addition, the balloon 114 (or balloon-like structure)may be made out of any of a wide variety of woven or nonwoven fibers,fabrics, metal mesh such as woven or braided wires, and carbon.Biocompatible fabrics or sheet material such as ePTFE and Dacron® mayalso be used.

[0082] The hardenable media is preferably a rapid setting, lowviscosity, liquid polymer or polymer precursor, such as polymethylmethacrylate. However, any of a variety of other materials which providethe required stiffening or setting characteristics may be used,including any of a variety of epoxies, polyurethane or blends ofpolyurethane-silicone.

[0083] In the context of a rod shaped inflatable container, for use inspinal fixation procedures, the physical requirements of the hardenablemedia will depend upon the length and diameter of the rod as well as thephysical requirements imposed by the implantation site. For certainembodiments, polymethyl methacrylate, epoxy, polyurethane or otherparticular material may or may not exhibit sufficient physicalproperties. Physical properties of a hardenable material can be modifiedthrough the addition of any of a variety of additives, such as carbonfibers, Kevlar or Titanium Rods, woven or laser etched metallic tubularstents, or other strength enhancers as will be understood in the art.The selection of a particular hardenable media, as well as thedesirability of adding strength, flexibility, or other physical propertyenhancers, can be optimized for any particular implantation systemthrough routine experimentation by those of skill in the art in view ofthe disclosure herein.

[0084] Certain composite materials, such as carbon fibers embedded in abonding agent such as a two part epoxy, or two part polyurethane havebeen found particularly useful in forming the implant of the presentinvention. For example, graphite (carbon fibers) having a diameterwithin the range of from about 0.003 to about 0.007 inches are providedin bundles (tows) composed of from about 3,000 to about 12,000 fibers.One typical fiber useful for this purpose is manufactured by HexcelCarbon Fibers, Salt Lake City, Utah, Part No. HS/CP-5000/IM7-GP 12K.Preferably, the Tow tensile strength is in the range of from about 5,000to about 7,000 Mpa. Tow tensile modulus is within the range of fromabout 250 to about 350 Gpa.

[0085] In certain embodiments, the fixation rods are formed without theneed of reinforcing fibers or rods. In such embodiments, the hardenablematerial itself exhibits physical properties sufficient for use in theimplants.

[0086] In general, the composite rods in accordance with the presentinvention will exhibit a static compression bending values (per ASTMF1717) within the range of from about 100 to about 200 lbs., and,preferably greater than about 150 lbs. The composite rods will exhibit astatic torsion (per ASTM F1717) within the range of from about 300 toabout 500 inch pounds, and, generally in excess of about 400 inchpounds. The rods will preferably reach at least about 5 million cycles,at 5 Hz. Each of these parameters may be measured in accordance with theprotocols described in the American Society for Testing and Materials(ASTM) designation F 1717-96, a copy of which is attached hereto asAppendix A, and which is incorporated in its entirety herein byreference.

[0087] Within the range of from about 30 to about 60 bundles of thecarbon fiber described above is packed in a deflated balloon, optionallyalong with a Ni—Ti stent having an 8 mm diameter and 8 cm length.Although any of a variety of stents may be utilized, one usefulstructure is similar to the Smart Stent (Cordis), and it helps keep thestructure intact and also adds structural strength to the implantedstructure.

[0088] A one or a two part epoxy having a viscosity in the range of fromabout 100 to about 1000 cps is then injected into the balloon underpressure such as by using a pump and pressure within the range of fromabout 4 ATM to about 10 ATM or more depending upon viscosity, balloonstrength and other design considerations. The pump is run for asufficient duration and under a sufficient pressure to ensure that theepoxy wets all of the fibers. This may range from about 10 minutes ormore to about an hour, and, in one application where the pump was run atabout 5 ATM pressure, requires at least about ½ hour. Specific methodparameters may be optimized depending upon the viscosity of the epoxy,infusion pressure, infusion flow rate, density of the packed carbonfibers, and other variables as will be apparent to those of skill in theart in view of the disclosure herein.

[0089] In an alternate embodiment, carbon fibers having within the rangeof from about 15 to about 45 degrees of braids are utilized. The braidmay be in the form of a plain weave, and may be obtained, for example,from Composite Structures Technology (Tehachapi, Calif.). A 0.5 inchdiameter of 45 degrees braided carbon fiber sleeve is positioned withinthe center of the balloon. This braided sleeve conforms dimensionally tothe inside diameter of the balloon. A 0.3 inch diameter braided carbonsleeve (again 45°×45° plain weave) may also be positioned concentricallywithin the balloon, within the outer braided carbon fiber sleeve.Unidirectional fibers are thereafter introduced inside of the ID of theinner braided carbon sleeve. Unidirectional fibers are also introducedinto the annular gap between the two braided sleeves. The volume of thefiber per volume of balloon is generally within the range of from about40% to about 55%. After placement of the foregoing structure within theportals of the screws, the epoxy mix having a viscosity within the rangeof from about 100 to about 1000 cps is injected under 10 atmospherespressure into the balloon.

[0090] Although the foregoing composite structure was described using acarbon fiber example, any of a variety of fibers may be positionedwithin the balloon to enhance the physical properties of the finishedproduct. For example, Kevlar fibers, PEEK, and any of a variety ofalternatives may be used. In general, the fibers will preferably providea very high tensile strength and high modulus, having a low diameter toenhance deliverability of the device.

[0091] The use of braided sleeves will produce higher structuralresistance to sheer stress as a result of torsional loads, plus theability to distribute unidirectional fibers in a homogenous mannerwithin the balloon at all times. This appears to improve the performanceof the implant.

[0092] One construction of a composite formable rod in accordance withthe present invention is illustrated in FIG. 4C. An outer balloon orother containment structure 114 is provided, as has been discussed. Areinforcing element 120 such as a stent is concentrically positionedwithin the balloon. An outer support tube 121 is positioned within thestent in the illustrated embodiment, however, the outer support tube 121can alternatively be positioned concentrically outside of the stent 120.The outer support tube 121, in one embodiment, is a 0.5 inch diameterbraided carbon fiber tube, having cross strands oriented at 45° angleswith respect to each other to improve torsion resistance as has beendiscussed.

[0093] An inner support tube 123 is spaced radially inwardly from theouter support tube 121. Inner support tube 123, in one embodiment,comprises a 0.3″ diameter braided carbon fiber sleeve havingcharacteristics described above. A first plurality of unidirectionalfibers 125 is axially oriented within the annular space between theouter support tube 121 and inner support tube 123. A second plurality ofunidirectional carbon fibers 127 is positioned within the inner supporttube 123.

[0094] Any of a variety of alternate constructions can be readilyutilized, in accordance with the teachings herein. For example, three ormore tubular support tubes may be utilized. The layering sequence of thevarious components may be changed, and other features added or deleteddepending upon the desired performance of the finished device. Inaddition, although the balloon 114 in one embodiment comprises a nylonsingle layer balloon, other materials may be utilized. In addition,multiple layer balloons may be utilized, with or without supportstructures such as stents, wires, or woven tubular support structuressandwiched therebetween.

[0095] In alternate embodiments, the formable rods do not include one ormore of the reinforcing structures illustrated in FIG. 4C. In one suchalternate embodiment, the first plurality of unidirectional fibers 125and the second plurality of unidirectional fibers 127 are not present.In another such alternate embodiment, the inner support tube 123, outersupport tube 121, and/or stent 120 are not present in the rod, which mayor may not contain fibers 125, 127.

[0096] Other embodiments comprise a containment structure such as anouter balloon or mesh, and have none of the aforementioned reinforcingstructures shown in FIG. 4C. In such other embodiments, the hardenablemedia alone suffices to form a rod having the needed strength and otherphysical characteristics. Embodiments that have few or no reinforcing orsupport structures are formed in substantially the same way as thosediscussed above, in that the hardenable media is injected into thecontainment structure in fluid form and then allowed to harden.

[0097] Marker bands made of materials such as gold, platinum or tantalummay also be positioned on the balloon, to facilitate fluoroscopicvisualization. Alternatively, a radio opaque material, such as tantalumpowder, may be sprinkled among the carbon fibers prior to infusion ofthe epoxy or other hardenable media, to allow visualization duringplacement.

[0098] The epoxy or the polyurethane material preferably has arelatively fast cure rate at 37° C. A low viscosity (no greater thanfrom about 100 to about 1000 cps) facilitates rapid transluminalintroduction through the delivery catheter and wetting of the relativelysmall interstitial spaces between adjacent carbon fibers. In addition,the polymer is preferably radiopaque. The polymerization is preferablyminimally exothermic, to minimize or prevent thermal damage to thesurrounding tissue. One epoxy which may be useful in the presentinvention is Epotek 301 available from Epoxy Technology, Inc.(Billerica, Mass.). This epoxy reaches 50 to 60% of its strength withinabout three to four hours following deployment, at 37° C. Using abonding agent having these approximate characteristics, the patient canbe restrained from rolling for an initial cure period of approximatelythree or four hours to achieve a partial cure (e.g., at least about 50%and preferably 60% or more), and be maintained in bed for a secondarycure period such as approximately the next eight to twelve hours or moreto accommodate a full cure. Other formulations of two part epoxies orpolyurethanes with faster cure times (preferably no more than about onehour full cure) can be formulated by changing the ratios of componentsand formulations for the catalysts. Cure time can also be acceleratedthrough the use of accelerators, such as catalysts or the application ofheat as is discussed in detail below.

[0099] In accordance with certain embodiments, preferred hardenablemedia have one or more of the following characteristics: (1) they curecompletely at a temperature that approximates that of an animal body(about 35-42° C.); (2) they exhibit mildly exothermic curing behavior,meaning that the media only self-heats due to the curing reaction to atemperature below about 45° C., preferably below about 42° C. so as toreduce the risk of heat damage to nearby living tissues during curing;(3) they exhibit little or no shrinkage of during curing so as tomaintain a tight fit following curing; (4) they have a pre-cureviscosity of preferably about 100-1000 cps, more preferably about100-400 cps; (5) they have a useful life (“potlife”) (i.e. have aviscosity low enough to allow for injection) of no more than about 30minutes after mixing/initiation/activation, preferably no more thanabout 15 minutes; (6) they are substantially cured (i.e. they arecapable of forming a rigid rod of material) preferably within about20-100 minutes or less, including within about 30, 40, 50, 60, 70, 80,and 90 minutes or less after initiation, such as by mixing; (7) theywill form a substantially cured rod having a static compression bendingvalue (per ASTM F1717) of at least about 60 lbs. (force), includingabout 70, 80, 90 and 100 lbs.; (8) they will form a fully cured rod(unreinforced) having static compression bending values (per ASTM F1717)within the range of from about 100 to about 200 lbs (force), preferablygreater than about 150 lbs, including about 110, 120, 130, 140, 160,170, 180, and 190 lbs., preferably within about 10-12 hours ofinitiation; (9) they will form a fully cured rod (unreinforced) having astatic torsion (per ASTM F1717) within the range of from about 300 toabout 500 inch pounds, preferably in excess of about 400 inch pounds;and (10) they will form a biocompatible solid. Especially preferredembodiments of hardenable media exhibit most or all of the foregoingcharacteristics.

[0100] One preferred family of hardenable media are two part epoxieshaving a very short cure time. The first part preferably comprises oneor more compounds bearing epoxide groups, preferably two or more epoxidegroups, and has a low viscosity. Preferred compounds include diepoxideresins having molecular weights between about 100 and 400, including,but not limited to, aromatic diepoxide compounds such as diglycidylether of Bisphenol A, and diglycidyl ether of Bisphenol F. Otherpreferred compounds include aliphatic epoxide resins, includingcycloaliphatic resins. One preferred class of aliphatic epoxide resinsare the diepoxide resins that are alkane diols of glycidyl ether,wherein the alkane portion is pentane, butane, propane, and the like.Such compounds generally have low viscosity (less than about 100 cp) andare sometimes called “reactive diluents” in that, when they blended withother epoxide materials, they serve to reduce the viscosity of themixture as well as react to form cross-links within the matrix of thecured epoxy. The first part may also comprise monofunctional epoxidemodifiers. In a preferred embodiment, the first part comprises a mixtureof aromatic diepoxide compounds and aliphatic diepoxide compounds.

[0101] The second part preferably comprises one or more curing agents orhardeners, including, but not limited to, aliphatic and cycloaliphatichardeners, mercaptan curing agents, and amine curing agents such asdiamines, triamines, tetramines, methylamines, ethylamines,propylamines, aminopiperazines, and other specialty amines. Preferredcuring agents or hardeners allow for cure of the media at ambient ornear ambient temperatures, preferably below about 45° C. Preferredcompounds include 1,3 diaminopropane, diethylenetriamine,triethylenetetramine, N-aminoethylpiperazine (includingN-aminoethylpiperazine nonyl/phenol from Air Products and Chemicals,Allentown, Pa.) and compounds according to the general formula:

[0102] wherein each R is independently selected from branched orunbranched chains of about 2-10, preferably 2-5, carbon atoms, and x is0, 1, or 2. In preferred embodiments, R is alkyl, preferably straightchained, and all R groups are the same. In some embodiments, the secondpart comprises a mixture of a cycloalkylamines, such as piperazine-basedamines, and alkylamines.

[0103] In accordance with a preferred embodiment, formulations compriseabout 60-80%, more preferably about 65-75% by weight of diepoxidecompounds (first part) and about 20-40%, more preferably about 25-35% byweight of amine curing agent (second part). In one embodiment, the firstpart comprises about 45-52% by weight aromatic diepoxide compounds andabout 19-23% by weight aliphatic diepoxide compounds, and the secondpart comprises about 20-29% alkyldiamines and about 4-9% by weightN-aminoalkylpiperazines. Five examples of formulations according topreferred embodiments are presented in Table 1 below. TABLE 1 QuantityFormulation Component (weight %) VL14M Part 1 Diglycidyl Ether ofBisphenol A 46.75% Butane Diol of Glycidyl Ether 20.00% Part 2n-aminoethylpiperazine nonyl/phenol 28.34% 1,3 diaminopropane 4.91% VL18Part 1 Diglycidyl Ether of Bisphenol A 49.12% Butane Diol of GlycidylEther 21.05% Part 2 n-aminoethylpiperazine nonyl/phenol 21.05% 1,3diaminopropane 8.78% VL18-3 Part 1 Diglycidyl Ether of Bisphenol A51.47% Butane Diol of Glycidyl Ether 22.06% Part 2n-aminoethylpiperazine nonyl/phenol 22.06% diethylene triamine 4.41%VL18-4 Part 1 Diglycidyl Ether of Bisphenol A 51.09% Butane Diol ofGlycidyl Ether 21.90% Part 2 n-aminoethylpiperazine nonyl/phenol 21.90%triethylene tetraamine 5.11% VL18-12 Part 1 Diglycidyl Ether ofBisphenol A 49.82% Butane Diol of Glycidyl Ether 21.35% Part 2n-aminoethylpiperazine nonyl/phenol 24.20% triethylene tetraamine 4.63%

[0104] For embodiments using other resins and/or hardeners, the amountsused, will need to be adjusted to maintain the stoichiometric ratios(epoxy groups to amino groups), as will be appreciated by those skilledin the art.

[0105] The first part and/or the second part may further comprise amaterial to lend radiopacity or fluoropacity to the media so that it ismore readily visualized during and after the procedure.

[0106] The hardenable material is made by mixing together the first andsecond parts. The first and second parts may be mixed prior to injectionor they may be mixed during injection, such as by use of a static mixeras is known in the art. In preferred embodiments,-the mixture isdegassed to remove any air bubbles that are formed during mixing.Removal of air bubbles, if present, will serve to reduce the viscosityof the mixture and will also help prevent the formation of voids in thecured rod that result from air bubbles in the hardenable media.

[0107] Terms such as “hardenable” or “curable” media are usedinterchangeably herein, and are intended to include any material whichcan be transluminally introduced through the catheter body into thecavity 146 while in a first, flowable form, and transitionable into asecond, hardened or polymerized form. These terms are intended to covermaterials regardless of the mechanism of hardening. As will beunderstood by those of skill in the art, a variety of hardening orpolymerizing mechanisms may exist, depending upon media selection,including hardening or polymerization due to exposure to UV or otherwavelength of electromagnetic energy, catalyst initiated polymerization,thermally initiated polymerization, and the like. Mechanisms such assolvent volatilization may also be used, but are disfavored due to thegreater likelihood of the formation of voids in the cured rod byevaporating solvent. While the media selection may affect catheterdesign in manners well understood by those of skill in the art, such asto accommodate outgassing of byproducts, application of heat, catalysts,or other initiating or accelerating influences, these variations do notdepart from the concept of the invention of introducing a flowable mediainto a shape and subsequently curing the media to the shape. Two partmedia, such as a two part epoxy or polyurethane, or a monomer and aninitiator may be introduced into the cavity 146 through separate lumenextending throughout the tubular body. Expandable media may also beprovided, such as a material which is implantable in a first, reducedvolume, and which is subsequently enlargeable to a second, enlargedvolume such as by the application of water or heat, or the removal of arestraint.

[0108] A study was undertaken demonstrating the low exotherm duringpolymerization or hardening of a rod according to a preferredembodiment. The study involved the use of two pigs. In the first pig, 8rods were implanted for mechanical strength studies. In the second pig,5 rods were implanted for conducting thermal studies. All the rods wereimplanted in the back muscle near the vertebral structure. Epoxyformulation VL-14 mixed with tungsten powder (1-5 micron size) wasinjected at a pressure of about 8 atm (about 118 Psi) into the balloonto form the rod 2-3 minutes after it was mixed using an Angioplastypump. Thermocouples were connected to the outside surface of the rodsimplanted in the second pig and a multichannel recorder connected to aPC monitored the temperature measured at the surface of the rod from theinjection (time 0) to 60 minutes following injection at intervals of oneminute. The data for one of the recorded channels is presented in FIG.53. The data obtained for the other channels was substantially similarto that presented in the figure. As can be seen in FIG. 53, the maximumtemperature reached was 40.5° C. The mechanical data obtained aftercuring period of 90 minutes resulted in an average of 93.5 lbf. formaximum bending compression strength for the construct as defined byASTM F-1717.

[0109] Various safety features to minimize the risk of rupture orleakage of the hardenable media may be utilized, depending upon designpreferences. For example, a two-layer or three-layer or more balloon maybe utilized to reduce the risk of rupture. In addition, the material ofthe single or multiple layers of the balloon may be selected to minimizeescape of volatile components from the curable media. In one embodiment,a double balloon is provided having a nylon inside layer and a PEToutside layer.

[0110] In addition, the inflation pressure of the curable media may beaffected by the nature of the balloon. For example, a polyethyleneballoon having a wall thickness of about 0.001″ may have a burstpressure of about 7 to 8 atmospheres. In that embodiment, an inflationpressure of no more than about 4 to 5 atmospheres may be desired. Aslightly higher inflation pressure, such as on the order of from about 5to about 6 atmospheres, may be utilized with a nylon balloon. Relativelynoncompliant materials such as PET have much higher burst pressures(range of 10-20 atmospheres), as is well understood in the balloonangioplasty arts.

[0111] In addition, the balloon contains a proximal valve as will bediscussed in additional detail below. Multiple valves may be utilized,in series along the flow path, to reduce the risk of failure and escapeof hardenable media. As a further safety feature, the deploymentcatheter may be provided with an outer spill sheath in the form of anelongate flexible tubular body which surrounds the deployment catheterand at least a proximal portion of the balloon. This spill sheathprovides an additional removable barrier between the junction of thecatheter and the balloon, and the patient. If a spill occurs during thefilling process, the spill sheath will retain any escaped hardenablemedia, and the entire assembly can be proximally retracted from thepatient. Following a successful filling of the balloon, the spill sheathand deployment catheter can be proximally retracted from the patient,leaving the inflated formable orthopedic fixation structure in place.

[0112] The reinforcing element 120 may be exposed to the interior cavity146 formed by the flexible wall 148, providing additional structuralintegrity. See, e.g., FIGS. 1 and 4C. The reinforcing element 120resists kinking of the balloon as the balloon is advanced around cornerssuch as during advancement through an aperture (e.g., portal or eyelet)on a bone anchor. The reinforcing element 120 may be positioned withinthe balloon 114. The reinforcing element may alternatively be embeddedwithin the wall of the balloon 114, or carried on the outside of theballoon much like a conventional stent. The reinforcing element 120 maybe an expandable tube, a slotted metal tube, reinforcing wires,straight, woven or braided fibers such as carbon fibers, or a stent andmay be provided with electrical conductors for completing a circuitthrough the deployment catheter, to generate heat and/or measuretemperature, as is discussed below. Certain preferred embodiments mayinclude a tube or wire. Reinforcement element 120 may comprise thin,reinforcing metallic wires, separate from the balloon wall. The wiresincrease the tensile strength of balloon 114 when inflated. Wires may betitanium, nitinol, elgiloy, or any other suitable material as known tothose of skill in the art.

[0113] The reinforcement element 120 may include an expandable tubularstent. A stent of any suitable type or configuration may be providedwith the delivery device, such as the Cordis artery stent (“smartstent”). Various kinds and types of stents are available in the market(Sulzer/Medica “Protege” stent and Bard “Memotherm” stent), and manydifferent currently available stents are acceptable for use in thepresent invention, as well as new stents which may be developed in thefuture.

[0114] Referring to FIGS. 4A and 4B, the illustrated elongate tubularbody 104 comprises an outer sleeve 112 and an inner sleeve 110 movablypositioned within the outer sleeve 112. The inflatable device 102 isremovably carried by or near the distal end 108 of the outer sleeve 112.Alternatively, the inflatable device 102 may be removably carried by theinner sleeve 110. The inner sleeve 110 may extend into the inflatabledevice 102, as illustrated.

[0115] The balloon 114 may be removably attached to the tubular body 104by a slip or friction fit on the distal end 108 of the outer sleeve 112or on the inner sleeve 110. A variety of alternative releasableattachments may be used between the outer sleeve 112 and/or inner sleeve110 and the proximal end 103 of the balloon 114, such as threadedengagement, bayonet mounts, quick twist engagements like a luer lockconnector, and others known in the art. In each of these embodiments, afirst retention surface or structure on the outer sleeve 112 and/orinner sleeve 110 releasably engages a complimentary surface or retentionstructure on the proximal end 103 of the balloon 114 as will be apparentto those of skill in the art.

[0116] The balloon 114 comprises a self-sealing valve 160 which preventsthe hardenable media from leaking once the delivery catheter 100 isdetached from the balloon 114. Valve 160 is provided for closing thepathway between inflation lumen 130 and inner cavity 146. Valve 160 maybe located at the proximal end 116 of inflatable device 102. A varietyof different valves may be used as will be recognized by those of skillin the art, such as a slit valve, check valve, duck-billed or flapvalve. A pierceable, self-sealing septum may also be used.Alternatively, a stopper may be provided which can be placed within thepathway to prevent leakage.

[0117] Referring to FIG. 7A, a duck bill valve is schematicallyillustrated. This valve includes at least a first, and preferably two ormore coaptive leaflets 161 and 163, which incline towards each other inthe distal direction as will be understood by those of skill in the art.Distal advancement of the inner sleeve 110 and/or pressurized mediathrough the valve 160 forces the coaptive leaflets 161 and 163 apart, tofacilitate introduction of the hardenable media. Upon removal of theinner sleeve 110, the coaptive leaflets 161 and 163 return to a closedconfiguration to inhibit or prevent the escape of hardenable media. Asingle leaflet 161 may be utilized, in the form of a flapper valve.

[0118] An alternate valve is illustrated in FIGS. 7B and 7C, and in anassembled device in FIG. 4B. In this valve, a tubular support structure165 is provided with a closeable cap 167. The closeable cap 167 may beformed from any of a variety of highly flexible polymeric materials,such as silicone, neoprene, latex, or others known in the art. Cap 167may be formed such as by dip molding or liquid injection molding,followed by the provision of a slit or potential opening 169.

[0119] The valve 160 may be connected to or formed with the inflatabledevice in any of a variety of manners, as will be appreciated in view ofthe disclosure herein. In the illustrated embodiment, the balloon 114 isprovided with a proximally extending neck 115 which carries the valve160 therein. The tubular body 165 having the cap 167 thereon ispositioned concentrically within the proximal neck 115, as illustratedin FIG. 4B. Alternatively, the valve 160 may be positioned within theballoon 114, i.e., distally of the proximal shoulder of the balloon 114.

[0120] Additional details of one detachable connection between thedelivery system and the implantable device is illustrated in FIG. 4B. Asillustrated therein, a tube 161 extends distally from the outer sleeve112. Tube 161 may comprise any of a variety of materials, which exhibitsufficient structural integrity for the intended use. In one embodiment,tube 161 is a metal hypotube having an inside diameter of about 0.085″to about 0.086 and a wall thickness of about 0.001″ to about 002″. Thetube 161 in the illustrative embodiment extends for a distance of about0.50 mm to about 0.75 mm beyond the distal end of the outer sleeve 112.

[0121] The tube 161 extends into a sliding fit with a tubular supportstructure 163 which may be positioned in a proximal neck portion of theballoon. When positioned as illustrated, the tube 161 ensures that thevalve 160 is open, so that the inner sleeve 110 may extend axiallytherethrough into the balloon.

[0122] In addition, the inside diameter of the tube 161 is preferablysufficiently larger than the outside diameter of the inner sleeve 110 toprovide an annular passageway in communication with the vent lumen 132.This structure ensures that the interior of the balloon remains incommunication with the proximal vent port by way of a vent lumen 132extending throughout the length of the assembly. In the illustratedembodiment, the outside diameter of the inner sleeve 110 is about 0.082″to about 0.084″, and the inside diameter of the tube 161 is about 0.085″to about 0.086″. Following infusion of the curable media into theballoon, the inner tube 110 and tubular body 161 are both proximallyretracted from the balloon, thereby enabling the valve 160 to close asis described elsewhere herein.

[0123] When fully inflated, as shown in FIG. 6, the balloon 114 has aninflated profile with a cylindrical working portion 140 having aninflated diameter located between a pair of conical end portions 142,144.

[0124] Referring to FIG. 9, at least one bone anchor 10 may be provided,such as that shown in FIG. 10. The bone anchor 10 includes a firstaperture 22, through which the orthopedic device 102 extends. A secondbone anchor 10 may also be provided including a second aperture 22,through which the orthopedic device 102 also extends. The first boneanchor 10 is preferably implanted within a first bone. The second boneanchor 10 may be implanted within the second bone. The bones may beadjacent vertebrae or first and second vertebrae spaced apart by one ortwo or more intermediate vertebrae.

[0125] The bone anchors of FIGS. 10-13 are made of a biocompatiblematerial such as titanium or stainless steel. Alternatively, boneanchors 10 may be made of a composite material. Bone anchors 10 may alsobe made of a suitable medical grade polymer. In one embodiment, boneanchors 10 have a length between about 40 mm and 60 mm, preferably about50 mm. However, the actual length is dependent on location of thefracture, size of patient, etc.

[0126] Bone anchor 10 comprises a proximal portion 12 having a proximalend 14 and a distal portion 16 having a distal end 18. Proximal portion12 typically comprises a head 20 and a portal 22. In a preferredembodiment, head 20 comprises a proximal portion 24 configured to matewith the tip of a screwdriver. Head 20 may comprise a standard orPhillips slot for mating with the screwdriver. A variety of slotconfigurations are also suitable, such as hexagonal, Torx, rectangular,triangular, curved, or any other suitable shape. The bone anchor of FIG.13 has a raised platform 25 having a plurality of substantially straightsides, such as a hexagonal platform, configured to mate with acorresponding depression in the distal end of a screwdriver. Platform 25may come in a variety of shapes suitable mating with a screwdriver.

[0127] Portal 22 of bone anchor 10 may extend through head 20 and isgenerally between about 4 mm and 8 mm in diameter, preferably about 6 mmto about 8 mm in diameter. Portal 22 may be of any shape suitable forreceiving inflatable, implantable orthopedic device 102; however, portal22 is preferably round.

[0128] Distal portion 16 of bone anchor 10 typically comprises threads26 and a sharp tip 28. Bone anchor 10 also preferably comprises acentral lumen 30 extending coaxially completely through bone anchor 10from proximal end 14 to distal end 18 and configured to receive aguidewire. Bone anchor 10 may also include at least one perforation 32,as shown in FIG. 13. Perforation 32 may be aligned axially, as shown, ormay be staggered axially. Perforation 32 permits bone to grow into boneanchor 10, stabilizing bone anchor 10 within the bone. Additionally,bone matrix material such as a hydroxyapatite preparation can beinjected into central lumen 30 and through perforation 32 to promotebone in-growth.

[0129]FIGS. 14 and 15 show screwdrivers 40 configured to apply torque tobone anchor 10. Screwdriver 40 comprises a proximal portion 42 having aproximal end 44 and a distal portion 46 having a distal end 48. Proximalportion 42 includes a handle 50 configured to permit grasping to applytorque to anchor 10. Various configurations of proximal end 44 arepossible. In the embodiment of FIG. 15, the proximal handles 50 may beindependently rotatable about their longitudinal axes.

[0130] Distal portion 46 comprises a shaft 52 having a tip 54 configuredto interface with proximal portion of bone anchor 10. Screwdriver 40 mayalso comprise a central lumen 55 extending coaxially from proximal end44 to distal end 48 configured to receive a guidewire.

[0131]FIG. 16 shows a guidewire directing device 60, which may be usedpercutaneously to alter the direction of an advancing guidewire.Guidewire directing device 60 comprises a proximal portion 62 having aproximal end 64 and a distal portion 66 having a distal end 68. Proximalportion 62 comprises a handle 70. Handle 70 is configured to assist ingrasping and manipulating guidewire directing device 60. The distalportion 66 comprises a shaft 72 having a fork-tipped end 68. Guidewiredirecting device 60 engages a guidewire at the fork-tipped end 68.Handle 70 is rotated, advanced, and withdrawn, thereby altering thedirection of the advancing guidewire.

[0132] A directing sheath 180, as shown in FIG. 17, may also be providedfor assisting in aligning the guidewire or delivery catheter to passthrough bone anchors 10. Directing sheath 180 comprises a proximalportion 182, a distal portion 184, and a central portion 186. Centralportion 186 includes at least two openings 188 sized substantially thesame as portal 22 of bone anchor 10. Directing sheath 180 preferablyincludes a lumen 190 extending through its entire length. Lumen 190 isof sufficient diameter to allow a structure such as a guidewire ordelivery catheter to pass through. Directing sheath 180 may be scoredalong its longitudinal axis, on either one line or two opposing lines192. Scoring 192 allows directing sheath 180 to be split into twoseparate halves by pulling the sheath apart at its proximal or distalend. Scoring 192 can be partially or completely through the sheath wall.

[0133] Directing sheath 180 is preferably formed from a biocompatiblepolymer. Directing sheath 180 may also include a radiopaque filament 194passing around each opening in central portion 186 or the entire lengthof sheath 180. Filament 194 aids in localizing directing sheath 180after percutaneous placement.

[0134]FIG. 44 illustrates the structure of an accelerator foraccelerating the curing of the curable media in one embodiment of theinvention. In this embodiment, the accelerator comprises a heating coil300 within the device 102 such as concentrically around the distal endof the inner sleeve 110 of the elongate tubular body 104 of a deliverycatheter 100. While the heating coil 300 is shown coiled around theexterior surface of the distal end of the inner sleeve 110, it can alsobe fitted inside the distal end of the inner sleeve 110, or embeddedwithin the distal end of the inner sleeve 110. The distal portion of thesleeve 110 may be provided with a detachable joint at the proximal end116 of the balloon 114 such that it is left behind within theimplantable device 102 following removal of the delivery catheter 100. Avariety of releasable attachments may be used, such as threadedengagements, bayonet mounts, quick twist engagements like luer lockconnectors, or others known in the art.

[0135] The accelerator is not necessary a part of the delivery catheter100. FIG. 45 schematically illustrates another embodiment in which theaccelerator is built into the inflatable orthopedic device 102. Asdisclosed above, a variety of structures may be provided asreinforcement element 120 in the cavity 146 of the balloon 114, such ascarbon fibers, titanium rods, or tubular stents. If the reinforcementelement 120 is made from electrically conductive materials, it can alsofunction as a resistive heating element. In FIG. 45 a metallic stent isillustrated. Titanium rods and carbon fibers may also be used.Electrical contacts 310 and 312 for conducting a current through thereinforcement element 120 are incorporated into the releasableattachment, such as a concentric sliding fit connection, used betweenthe outer sleeve 112 and/or inner sleeve 110 and the proximal end 103 ofthe balloon 114. These electrical contacts engage complimentary contactson the outer sleeve 112 and/or inner sleeve 110 to complete an electriccircuit with a proximally located power supply for running the resistiveheating element.

[0136] In order to accomplish the objective of acceleratingpolymerization of the epoxy or other hardenable media, the heatingelement preferably elevates the temperature of the epoxy to a pointabove normal body temperature. Temperatures at the heating element of atleast about 430, preferably at least about 50°, and, under certaincircumstances as high as 60° C. or more are desirable to produce anoptimal cure rate. However, the outside of the implant is preferably notheated to the extent that it causes localized tissue necrosis. Tissuenecrosis occurs at approximately 45° C. Thus, the heat source preferablysets up a temperature differential between the surface of the implantand the interior of the implant. This may be accomplished in severalways, such as, for example, selecting materials and thickness of theouter flexible wall 148 to provide thermal insulation of the adjacenttissue from heat generated by the heating element. As an alternative orin addition, heat sink structures may be provided at or near the outersurface of the orthopedic device 102. A flow path such as an annularspace formed within a double walled balloon may be utilized to circulatea coolant such as saline or other circulating cooling fluid. Suchmeasures preferably permit the heating element to be heated as high as50° C. or higher, while maintaining the outside surface of the device102 at a temperature of no more than about 45° C., and, preferably nomore than about 43° C.

[0137] Excessive temperature can also be reached transiently, such as atthe beginning of a heating cycle when the temperature may temporarilyovershoot the 45° C. desired maximum. The present inventors havedetermined that the initial temperature overshoot can be eliminated orreduced by appropriately driving the power to the heating element as isdiscussed in detail below. The driver circuitry preferably brings theheating element up to operating temperature rapidly, while minimizingthe risk of thermal overshoot beyond a predetermined maximum. All of theforegoing measures preferably allow a sufficient curing of thehardenable media to limit the required period of immobility to no morethan about 2 hours, preferably no more than about 1 hour and, optimallyno more than about 45 minutes post implantation. Although a completecure is not required within this time window, a sufficient cure isdesirable that the patient need not be immobilized beyond the initialcure. Thereafter, the hardenable media will continue to harden, such asover the next few hours or even days, but with little or no restrictionon the patient's activities.

[0138] The resistive heating element, whether the heating coil 300, thereinforcement element 120, or other structure, may be made from materialwith either a positive or negative temperature coefficient ofresistance, e.g., electrical resistance either directly or indirectlyproportionate to temperature, respectively. The temperature may bemonitored by measuring the DC voltage across the resistive heatingelement, for the voltage is directly proportional to resistance for agiven current, and the temperature coefficient of resistance is known.Alternatively, by measuring the voltage, current and phase of the drivesystem, the resistance of the heating element and thus its temperaturecan be calculated by a microprocessor or dedicated circuitry.

[0139] Alternatively a thermistor 314 may be used to monitor thetemperature of the inflatable orthopedic device 102. Thermistors arewell known in the art. Using one or more separate thermistors 314 wouldentail more electrical contacts (not shown) as another electrical loopin addition to the one running the heating element may be necessary.Other methods of measuring the temperature include the use of an opticalfiber in conjunction with a thermally reactive material, a coaxialplunger in conjunction with a thermal bulb, or a semiconductortemperature sensor or junction (such as a diode) carried by theorthopedic implant. A bimetallic heating element may function similarlyto a circuit breaker and self-regulate.

[0140]FIG. 46 illustrates one embodiment of the control panel 316 forthe heating element 300, in electrical communication with cathetermanifold 124. The heating cycle selected and the time elapsed/remainingin the cycle are displayed. Each heating cycle is associated with aheating profile, a table of target temperatures at different points oftime in the heating cycle. A button may be used to toggle the displaybetween elapsed and remaining time. There is also a power switch, aselector for the heating cycle, and a run/pause button to interrupt theheating cycle. LED's or other indicators may be used to indicate whetherthe heating cycle is running or paused. LED's may also be used toindicate the status of the battery—low, charging or full, the status ofthe control block—on or off, and the status of the heatingelement—heating or not. The heating indicator is preferably configuredto light when the heating element is first active, and blink when thetemperature of the heating element is regulated via the heating profile.Ideally the control block 324 is provided with circuitry that detectsfaults and problems with the connection. These problems may becommunicated to the user via LED's and/or audible alarms.

[0141] The illustrated embodiment of the control panel 316 has a cyclebutton 600 with which to select the heating cycle, and a cycle window602 to display the cycle selected. The control panel 316 is alsoprovided with a pause switch 604 to pause the heating cycle, and LED's606 and 608 respectively to indicate whether the cycle is running orpaused. A time window 610 indicates the time elapsed in the heatingcycle. An optional toggle switch (not shown) may be used to toggle thetime window 610 to display the time remaining in the heating cycle. Apower switch 612 turns the control panel on and off while a power LED614 displays its power status. A heating LED 616 indicates whether theheating cycle is in a heating phase. Warning LED's 618 indicate whetherthere is a fault in the circuitry or connection with the heating element300. Battery LED's indicate the charge status of the battery.

[0142]FIG. 47 is a simple block diagram of a control circuitry of theheating element in one embodiment. This circuit allows optimization ofthe heating cycle, by heating the heating element rapidly to the desiredtemperature but minimizing the risk of a thermal overshoot beyond thetarget temperature which would have created a risk of thermally inducednecrosis. A start switch 320 begins a heating cycle and a timer 322. Acontrol block 324, controlled via the control panel 316, stores aheating profile and controls the circuitry described below. Aprogrammable pulse width modulated power source is used as a highfrequency power generator 326 to supply power, through a high-passfilter 328 to the heating element 330. The high frequency powergenerator 326 ideally operates at a frequency above the biologicalbandwidth. While any circuitry operating at frequencies above 2 kHzwould fit this description, frequencies above 10 kHz are preferable. Inone embodiment the high frequency power generator 326 operates at 125kHz, and in another it operates at 128 kHz.

[0143] Low-pass filters 332 isolate the high frequency power generator326 from a precision current source 334 and an amplifier 336. Theprecision current source 334 feeds a low precise DC current through theheating element 330. The resulting DC voltage across the heating element330 is amplified by the amplifier 336 and compared against a referencevoltage generated by a reference module 338. The comparison is done by alevel comparator 340. As voltage is directly proportionate to resistanceat a given current, the resistance across the heating element 330 canthus be measured. With the temperature coefficient of resistance of theheating element 330, the temperature of the heating element 330 can thusbe calculated. The control block 324 acts on feedback from thecomparator 340 to enable or disable the high frequency power generator326, and thus regulate the temperature of the heating element 330according to the heating profile. In one embodiment a clinicalpractitioner may have the option of overriding the heating profile byinputting the desired temperature into the control block 324 directly.While a resistive heat source has been described in some of the aboveembodiments, other energy sources to accelerate the curing of thecurable media may be used. These include, but are not limited to, addinga polymerizing agent, radio frequency, ultrasound, microwave and lasers.Also, the complete curing of the curable media by the describedapparatus and methods is not always required to occur beforediscontinuing the heat source or other initiator step in theseembodiments. When the curable media has been partially cured to acertain level of structural integrity, the patient does not have to beretrained for the remaining cure time necessary to achieve a completecure. Thus the period of patient immobilization is minimized using thecuring accelerators of the present invention.

[0144] Another specific embodiment is described in connection with FIGS.48 through 51. Although certain specific materials and dimensions willbe disclosed below, these are exemplary only and may be varied as willbe understood by those of skill in the art. FIG. 48a is an overview of aheated inflatable orthopedic balloon 400. The distal end 402 of theballoon 400 is sealed with a silicone adhesive. This silicone adhesivealso holds the distal marker 404 in place. The distal marker 404 may bemade of various materials, including gold, platinum or tantalum. Aninner tubing 406, made of PET, runs from the distal tip 402 along theaxis of the balloon 400 to the proximal end. The inner tubing 406 isporous, to allow the curable media to flow radially outwardlytherethrough. A heating element 408, such as a coated tungsten wire, iscoiled around the inner tubing 406. In the illustrated embodiment, theheating element 408 is coiled in a parallel double-stranded fashionaround the inner tubing 406, with the two strands joined in a loop 410towards the distal end 402 to form a continuous electrical pathway.Carbon fibers are provided in the space 412 between the inner tubing 406and the outer wall 414 of the balloon 400. The carbon fibers may have adiameter of between 0.003 to 0.007 inches. They are bundled in tows ofabout 3,000 to about 12,000 fibers. A typical carbon fiber suitable forsuch use is made by Hexcel Carbon Fibers, Salt Lake City, Utah, Part No.HS/CP-5000/IM7-GP 12K. Tow tensile strength in the range of about 5,000to about 7,000 Mpa may be achieved. Tow tensile modulus may be withinthe range of about 250 to 350 Gpa. As noted above, in embodimentswherein the hardenable media alone has sufficient strength, the carbonfibers may be omitted.

[0145]FIG. 48b is an enlarged view on the proximal portion of theballoon 400. The inner tubing 406 terminates at about the proximal end416 of the balloon 400. The proximal end 416 comprises a nylon tubularsupport structure 417. Both the proximal marker 418 and the valveassembly 420 are held in place in the tubular support 417 by a siliconeadhesive. Two concentric electrical connector rings are also supportedby the support structure 417. The inner electrical connector ring 422 issmaller in diameter, and located more distally, than the outerelectrical connector ring 424. Each end of the heating element 408 iselectrically joined to one of these electrical connector rings. A seal426 is provided at the proximal tip of the tubular support 417. Theproximal end 416 is shaped with an annular reduction in diameter suchthat a bottleneck 428 is formed just distal of the seal 426.

[0146]FIG. 48c is an end view of the proximal end 416 along the axis ofthe balloon 400.

[0147]FIG. 49 is an enlarged view of the distal end of the catheter,with the balloon 400 removed. The innermost tube is the injection tube430. The lumen therein is the injection lumen 432. The injection lumen432 extends proximally to an injection port on the proximal end of thecatheter. The injection tube 430 is coaxially arranged within thesuction tube 434. An annular space between the outside surface of theinjection tube 430 and the inside surface of the suction tube 434defines the suction lumen 436. The suction lumen 436 communicates with asuction port on the proximal end of the catheter.

[0148] The inner electrical connector tube 438 is coaxially carried bythe exterior perimeter of the suction tube 434. The outer electricalconnector tube 440 is coaxially arranged around the exterior perimeterof the inner electrical connector tube 438. A layer of electricalinsulation is provided between the two electrical connector tubes 438and 440. This can be accomplished by coating the inner surface of theouter electrical connector tube 440 or the outer surface of a proximalportion of the inner electrical connector tube 438 with an electricallyinsulating material, such as polyurethane or PTFE. Both electricalconnector tubes 438 and 440 may be slotted to ease connection, asdiscussed below. A wire connects each electrical connector tube to thedrive circuit of the heating element 408. Each electrical connector tubemay have an additional wire connected to it, which may be used togetheras a dedicated feedback loop to more accurately measure the electricalresistance of the heating element 408. A spacer tube 442 is providedwith a notch 443 which provides an annular seat for the proximal end ofthe outer electrical connector 440, to hold the outer electricalconnector tube 440 in place.

[0149] A lock tube 444 is coaxially arranged around the exteriorperimeter of the spacer tube 442. The lock tube 444 is provided with oneor two or more axially extending slits 445 and provided with a radiallyinwardly extending projection 446 for releasable engagement with acorresponding annular recess on the proximal end of the balloon 400, asdiscussed below. The inner tube 448 holds the suction tube 434 and theinjection tube 430, as all three extend all the way proximally into thecatheter handle. The outer tube 450 terminates proximally at a luer lockat the distal end of the catheter handle.

[0150]FIG. 50 illustrates the proximal connections of the injection tube430, the suction tube 434, the inner tube 448 and the outer tube 450 tothe catheter handle 500. As discussed above, the injection tube 430 isconnected to an injection port 502. The suction lumen 436, defined bythe space between the injection tube 430 and the suction tube 434, opensinto the suction port 504. The inner tube 448 extends into the catheterhandle 500, while the outer tube 450 terminates at a luer lock 506 atthe distal end of the catheter handle 500. The wires connecting theelectrical connector tubes 438 and 440 are routed through an electricalport 508. A luer lock 510 allows both injection tube 430 and suctiontube 434 to be removed from the catheter following injection of acurable medium into the balloon 400, as will be discussed below.

[0151] Referring to FIGS. 48a, 48 b, 49, and 50, the attachment of thecatheter to the balloon 400 is now described. As described above, theinjection tube 430 and the suction tube 434 of the catheter are coaxial,with the injection tube 430 inside the suction tube 434. The injectiontube 430 extends through the inner tubing 406 into or close to thedistal end 402 of the balloon 400. The suction tube 434 extends throughthe valve assembly 420 of the balloon 400 to a point just distal of theproximal marker 418. The valve assembly 420 thus seals around theexterior surface of the suction tube 434.

[0152] When the catheter is attached to the balloon 400, the innerelectrical connector tube 438 contacts the inner electrical connectorring 422, and the outer electrical connector tube 440 contacts the outerelectrical connector ring 424. As described above, both electricalconnector tubes are slotted to ease their insertion into the respectiveelectrical connector rings. These two contacts complete the electriccircuit between the heating element 408 and its drive circuitry.

[0153] The lock tube 444 holds the balloon 400 in place at the end ofthe catheter. A seal 426 at the proximal end 416 of the balloon 400seals against the interior surface of the lock tube 444. As describedabove, the lock tube 444 is slit to ease its insertion over the proximalend 416 of the balloon 400. One or more radially inwardly extendingprojections 446 provided on the interior surface of the lock tube 444complements the bottleneck 428 in the proximal end 416 of the balloon400 to provide an interference engagement which is maintained by theouter tube 450. The outer tube 450 may be released via the luer lock506, allowing it to slide distally over the lock tube 444 to restrainthe projection 446 of the lock tube 444 within the bottleneck 428 of theballoon 400.

[0154] Any of a variety of releasable connectors may be utilized,between the catheter and the implant. For example, threaded connections,twist locks, interference fit and friction fit structures are well knownin the art. In general, a releasable connection which will withstandsufficient tension and compression during the positioning process ispreferred. Such structures will generally include an interference fit.In the illustrated embodiment, a radially inwardly extending annularridge which is provided with two or more axially extending slots toallow lateral movement cooperates with a radially inwardly extendingannular recess on the proximal end of the implant as has been discussed.The radially inwardly extending ridge provides an interference surface,which may also be carried by one or more lever arms or other supportstructures. The relationship may alternatively be reversed between thedeployment catheter and the implant, such that one or more radiallyoutwardly extending projections on the implant engage a radiallyoutwardly extending recess on the interior wall of the deploymentcatheter. In general, a positive interference fit can be readilyaccomplished by a first locking surface on the catheter which isremovably engaged with a second, complementary locking structure on theimplant. Preferably, one of the first and second locking structures islaterally moveable to engage and disengage the implant, and a lock isprovided for releasably locking the first and second engagement surfacesto releasably retain the implant on the catheter.

[0155]FIG. 51 illustrates the proximal end of the balloon 400 attachedto the distal end of the catheter as described above.

[0156]FIG. 52 illustrate an embodiment of a stiffening wire 520 used tofacilitate the insertion of the catheter. The stiffening wire 520comprises an elongate flexible body, having a proximal end and a distalend. A handle 522 is provided at its proximal end. The length of thewire is sufficient to provide support to the catheter during insertion,and thus may be varied depending on the catheter dimensions which arediscussed elsewhere herein. Diameters are also based upon the ID of theinflation lumen of the intended catheter. In one embodiment, the wirecomprises an 0.050 inch OD wire or tube, which may be stainless steel orother material. A lubricious coating, such as PTFE may also be provided.To achieve more flexibility in distal region 524, the wire or tube maytaper throughout a tapered zone 528 to a smaller OD distally. A coilspring 526 may be carried concentrically around the tapered zone 528,and attached at a distal tip 530. This allows the guide wire to beincreasingly flexible distally.

[0157] The deployment and release of the inflatable orthopedic balloon400 is now described. A guide wire may be inserted into the injectionlumen 432 to stiffen the entire catheter to facilitate insertion of theballoon 400. This guide wire may be inserted via the injection port 502.Ideally this guide wire extends all the way to the distal end 402 of theballoon, and has a diameter that permits axial movement within the innerdiameter of the injection tube 430. The insertion of the balloon 400 maybe visualized by fluoroscopy of the distal marker 404 and the proximalmarker 418. The guide wire is removed prior to the injection of curablemedium into the balloon 400 via the injection lumen 432.

[0158] The injection port 502 is then connected to a pump, which pumpscurable medium into the balloon 400 through the injection tube 430. Asthe injection tube 430 in the illustrated embodiment extends through theinner tubing 406 into or close to the distal end 402 of the balloon 400,the balloon is filled from the distal end 402 first. A vacuum isconnected to suction port 504. As described above, the suction tube 434extends through the valve assembly 420 of the balloon 400 to a pointjust distal of the proximal marker 418, and the inner tubing 406 of theballoon 400 is porous. This suction thus contributes to the filling ofthe balloon 400 with curable medium.

[0159] After the space 412 (as defined by the volume between the innertubing 406 and the outer wall 414 of the balloon 400) is filled withcurable medium, the luer lock 510 may be disengaged to allow the removalof the injection tube 430 and the suction tube 434. Any space remainingin the inner tubing 406 is filled with curable medium as the injectiontube 430 is slowly pulled out. The valve assembly 420 of the balloon 400prevents any curable medium from leaking.

[0160] For those embodiments in which heating is used to accelerate thecuring of the hardenable media, a high frequency current is passedthrough the heating element 408 to accelerate the curing of the curablemedium in the balloon 400, as has been discussed above in FIG. 47.

[0161] After the completion of the heating cycle (if performed), thecatheter is removed from the balloon 400 by first sliding outer tube 450proximally, exposing the lock tube 444. As described above, the locktube 444 is slit. Without the outer tube 450 around it, the roundedproximal surface of projection 446 of the lock tube 444 will slide overand off the bottleneck 428 of the balloon 400 as the catheter handle 500is pulled proximally. This action will also disengage the innerelectrical connector tube 438 from the inner electrical connector ring422 and the outer electrical connector tube 440 from the outerelectrical connector ring 424. The balloon 400 is thus left in placeafter the removal of the catheter.

[0162] Although the application of the present invention will bedisclosed in connection with connecting two adjacent vertebrae, themethods and structures disclosed herein are intended for various otherapplications such as to connect three or more vertebrae, as will beapparent to those of skill in the art in view of the disclosure herein.In addition, the method may be used to stabilize the L5 vertebrae, usingthe cranial-ward portion of the sacrum as the vertebrae with which L5 isanchored. Furthermore, although the method is disclosed and depicted asapplied on the left side of the vertebral column, the method can also beapplied on the right side of the vertebral column, or both sides of thevertebral column sequentially or simultaneously.

[0163] The method of the present invention involves percutaneouslyinserting one or more fusion devices into two or more than two adjacentvertebrae, either unilaterally or, preferably bilaterally, where aportion or all of at least one of the vertebrae is unstable, separatedor displaced. The fusion devices reposition or fix the displacedvertebra or portion of the displaced vertebra to a position within thevertebral column which is more stable or which causes less morbidity.

[0164] Referring now to FIG. 18 through FIG. 28, there are shown aseries of drawings depicting various stages of the method ofrepositioning and fixing a displaced vertebra or portion of a displacedvertebra, unilaterally, according to the present invention. FIGS. 18-28show partial cutaway, perspective, midline sagittal views of a portionof a vertebral column undergoing the method of the present invention.

[0165] The method will now be disclosed and depicted with reference toonly two vertebrae, one which is either unstable, separated or displacedand one of which is neither unstable, separated nor displaced. However,the method can also be applied to three or more vertebraesimultaneously, as will be understood by those with skill in the artwith reference to this disclosure. Additionally, the method can be usedto stabilize the L5 vertebrae, using the cranial-ward portion of thesacrum as the “vertebrae” with which L5 is anchored. Further, though themethod is disclosed and depicted as applied on the left side of thevertebral column, the method can also be applied on the right side ofthe vertebral column or, preferably, can be applied on both sides of thevertebral column, as will be understood by those with skill in the artwith reference to this disclosure.

[0166] First, the present method comprises identifying a patient who isa suitable candidate for undergoing the method. In connection with aspinal application, a suitable candidate has one or more unstablevertebrae, one or more portions of one or more vertebrae at least partlyseparated from the remainder of the vertebrae, one or more portions ofone or more vertebrae at least partly separated from the remainder ofthe vertebrae with potential or complete separation, or has one or morevertebrae or a portion of one or more vertebrae displaced from itsnormal position relative to the vertebral column, or has one or moreportions of one or more vertebrae at least partly separated from theremainder of the vertebrae and displaced from its normal positionrelative to the vertebral column. Further, the suitable candidate willnormally have either pain, loss of function or real or potentialinstability which is likely due to the separation or displacement, orseparation and displacement. If only a portion of the vertebra isunstable, separated or displaced, the portion of the vertebra that isunstable, separated or displaced will generally include at least part ofthe vertebral body and adjoining pedicle. However, other unstable,separated or displaced portions of a vertebra can be repositioned orfixed using the present method, as will be understood by those withskill in the art with reference to this disclosure. For example, asuitable patient can have a disease or condition such as spondylosis,spondylolisthesis, vertebral instability, spinal stenosis anddegenerated, herniated, or degenerated and herniated intervertebraldiscs, though actual indications require the expertise of one of skillin the art as will be understood by those with skill in the art withreference to this disclosure.

[0167] Next, the present method comprises making a stab incision in thepatient's skin overlying the patient's vertebral column at or near thelevel of the vertebrae or portion of vertebrae to be repositioned orfixed. In one embodiment, the incision is made at or near the level ofthe pedicle of the vertebra or portion of vertebra to be repositioned orfixed. The pedicle level is located preferably by identifying thepedicle shadow using fluoroscopy. In a preferred embodiment, the stabincision is made using a #11 scalpel blade.

[0168] Then, as shown in FIG. 18, an 11-gauge bone biopsy needle 202 orits equivalent is placed through the stab incision to create a tract tothe posterior periosteal surface of the vertebra 200 which is to bestabilized, repositioned or fixed. Next, the biopsy needle 202 is usedto make a small incision in the periosteum and into the cortex of thevertebrae.

[0169] Then, as shown in FIG. 19, a rigid, needle-tipped guidewire 204having a diameter in the range of 0.035″ to about 0.060″ is insertedthough the biopsy needle 202 into the tract, through the periostealincision and into the cortex of the bone, and the guidewire 204 isadvanced into the anterior aspect of the vertebral body 200 or intoanother suitable portion of the vertebrae 200, as will be understood bythose with skill in the art with reference to this disclosure. Insertionof the guidewire 204 is preferably accomplished using fluoroscopy. Thisprocess creates a continuous tract from the skin surface into theanterior vertebral body or suitable portion of the vertebrae 200.

[0170] The biopsy needle 202 is then removed and the tract from the skinsurface to the nicked periosteal surface is enlarged by using ahigh-pressure fascial dilator balloon (not shown) over the needle-tippedguidewire. Then, the balloon is removed and a working sheath 206 isintroduced into the dilated tract. Alternately, a hard plastic ormetallic sheath with a central dilator is advanced over the guidewirefrom the skin surface to the periosteal surface. Next, a pilot hole maybe drilled using an over-the-wire drill bit driven by a hand held drill.

[0171] Next, as shown in FIG. 20, a bone screw 208 according to thepresent invention is introduced into the working sheath 206 over theguidewire 204 by introducing the central lumen of the bone screw 208over the proximal end of the guidewire 204. A screwdriver 210 accordingto the present invention is similarly introduced over the guidewire 204.The bone screw 208 and distal portion of the screwdriver 210 are thenadvanced distally through the sheath 206 and the tract to the periostealsurface of the vertebral 200 until the proximal portion of the bonescrew 208 is engaged by the tip of the screwdriver 210. Torque isapplied to the bone screw 208 using the screwdriver 210 and the bonescrew 208 is advanced until the distal portion of the bone screw 208enters the anterior vertebral body or other suitable portion of thevertebra 200, while the portal of the bone screw 208 is exterior anddorsal to the vertebra 200 and the portal is open parallel to the longaxis of the vertebral column. Then, as shown in FIG. 21, the guidewire204, sheath 206 and screwdriver 210 are removed after satisfactoryplacement of the bone screw 208 has been obtained and confirmed byfluoroscopy. Additionally, bone matrix material such as a hydroxyapatitepreparation can be injected into the central lumen of the bone screw andthrough the one or more than one perforation, if present, to promotebone ingrowth.

[0172] The stages discussed above are repeated for at least oneadditional vertebra 212 until each vertebra that is to be repositionedor fixed has a bone screw 208 applied, and additionally for at least onevertebra which is neither unstable, separated nor displaced and whichlies adjacent the cranial-most or caudal-most vertebra that is beingrepositioned or fixed. The bone screw 208 placed into the vertebra 212which is neither unstable, separated nor displaced is used as the anchorto reposition or fix each vertebra 200 which is unstable, separated ordisplaced as follows. As will be understood by those with skill in theart with reference to this disclosure, the bone screws can be placedinto the vertebrae in a different order to that described above.

[0173] After a bone screw is positioned in each vertebra, the portalsare connected using an inflatable connection rod according to thepresent invention where the rod is inserted between the portals of thebone screws and inflated to create a rigid structure with the bonescrews, thereby repositioning and fixing the one or more than onepreviously unstable, separated or displaced vertebra, or one or morepreviously unstable, separated or displaced portions of one or morevertebrae with the vertebra that is neither unstable, separated nordisplaced. Connection of the bone screws with the inflatable rod isaccomplished as follows.

[0174] Referring now to FIG. 22 and FIG. 23, a hollow needle 214, suchas a 16 gauge or 18 gauge needle, is inserted percutaneously andfluoroscopically advanced to the portal of one of the bone screws 208.While the hollow needle is shown engaging the bone screw 208 in thecranial-ward vertebrae 212, the hollow needle can engage the bone screw208 in the caudal-ward vertebrae 200 first, as will be understood bythose with skill in the art with reference to this disclosure. FIG. 23is a detailed view of FIG. 22.

[0175] Then, as shown in FIG. 24, a needle-tipped, semi-rigid guidewire216 is introduced through the lumen of the hollow needle 214 and intothe portal of the bone screw 208 in the cranial-ward vertebrae 212. Thehollow needle 214 preferably has a Tuohy needle tip which causes theguidewire 216 to exit the hollow needle 214 perpendicular to thedistal-proximal axis of the bone screw 208 and parallel to the long axisof the vertebral column. Alternately, the hollow needle 214 can have anangled-tip modified Ross needle or other suitable structure as will beunderstood by those with skill in the art with reference to thisdisclosure.

[0176] In one embodiment, as further shown in FIG. 24, a guidewiredirecting device 218 according to the present invention is insertedpercutaneously between the portals of each bone screw 208 and thefork-tipped end is used to direct the advancing guidewire 216 throughthe second bone screw portal, and to reorient the guidewire 216 afterthe guidewire 216 has passed through the portal on the bone screw 208 ofthe caudal-ward vertebrae 212.

[0177] In another embodiment, as further shown in FIG. 24, a guidewirecapture device 219, such as a snare or grasping forceps, is insertedpercutaneously, caudal to the portal of the bone screw in thecaudal-ward vertebrae. The capture device 219 engages the guidewireafter it passes through the portal of the bone screw in the caudal-wardvertebra and allows the distal end of the guidewire to be pulled throughthe skin posteriorly to obtain control of both the proximal and distalends of the guidewire.

[0178] In another embodiment, the needle-tipped, semi-rigid guidewire216 comprises an outer helical, flat wire sheath and an innerretractable sharp tip stylet. Once the needle-tipped, semi-rigidguidewire is placed, the stylet can be removed to allow for easiercapture by the capture device with less trauma to the surroundingtissue.

[0179] Then, as shown in FIG. 25, the entire guidewire tract is dilatedusing a high pressure balloon and a flexible introducer sheath 220 maybe passed over the guidewire 216 along the entire guidewire tractexiting the caudal-ward stab incision. The guidewire 216 is removedafter the introducer sheath 220 is placed. Alternatively, the implant isadvanced over the wire 216 without the use of a sheath 220.

[0180] Next, as shown in FIG. 26, an uninflated, inflatable connectionrod 222 according to the present invention which is attached to aproximal pushing catheter 224 is advanced through the introducer sheath220 until the inflatable connection rod 222 advances between the twoportals and the proximal end of the inflatable connection rod 222 liescranial to the portal on the bone screw 208 in the cranial-ward vertebra212 while the distal end of the inflatable connection rod 222 liescaudal to the portal on the bone screw 208 in the caudal-ward vertebra200. The sheath 220 is removed and the placement is confirmed byfluoroscopy.

[0181] Then, as shown in FIG. 27, the balloon of the inflatableconnection rod 222 is inflated with a rapid setting, curable media suchas liquid polymer, or its equivalent, and the polymer is allowed to setfixing each bone screw 208 in relation to each other and repositioningand fixing the vertebra 200 or portion of the vertebra that wasunstable, separated or displaced. In one embodiment, the liquid polymeris or includes a two part epoxy or other hardenable media such as thosediscussed elsewhere herein, and curing is optionally accelerated by theapplication of heat. The inflated balloon of the inflatable connectionrod 222 expands radially beyond the diameter of the portals of each bonescrew 208 which helps fix the bone screws 208 in relation to each other.

[0182] Finally, as shown in FIG. 28, the delivery or pushing catheter224 is detached from the inflatable connection rod 222 by pulling on thepushing catheter 224 while resisting proximal movement of the inflatableconnection rod 222 to disengage the inflatable connection rod 222 fromthe pushing catheter 224 and the pushing catheter 224 is removed. Theinflatable connection rod 222 comprises a self-sealing valve whichprevents the polymer from leaking once the pushing catheter is detached.The vertebra is then fixed unilaterally. The method can be repeated onthe opposite side of the spinous processes of the patient's vertebraecolumn, thereby repositioning or fixing the one or more unstable,separated or displaced vertebrae or the one or more portions of one ormore vertebrae bilaterally. The access incisions are closed or sealed asnecessary and routine postoperative care administered.

[0183] Referring now to FIG. 29, there is shown a posterior perspectiveview of a portion of a vertebral column which has had some vertebraerepositioned and fixed bilaterally according to the present invention.When bilateral fixation is accomplished, it is preferred to place allbone screws before connecting the portals with inflatable connectionrods.

[0184] In another embodiment of the present method, a directing sheath180 according to the present invention is advanced over a guidewireuntil the openings in the directing sheath 180 overlie the position ineach vertebra which will receive a bone screw 208. The bone screws 208are then placed as disclosed in this disclosure, but through theopenings in the directing sheath 180, which aligns the lumen in thedirecting sheath with the portals of the bone screw 208. Then (notshown), a guidewire is inserted into the lumen of the directing sheathat the proximal end of the directing sheath and advanced until theguidewire passes through each portal of the bone screws and exits thebody through the lumen of the directing sheath at the distal end. Thedirecting sheath is then removed by peeling the sheath apart along thescored lines and pulling the two halves out from the body. The guidewirethat was in the lumen of the directing sheath remains in place to guidethe placement of the uninflated, inflatable connection rod. Alternately,the uninflated, connection rod can be inserted directly into the lumenof the directing sheath at the proximal end and advanced until theuninflated, inflatable connection rod is properly positioned between theportals of the bone screws. Referring now to FIGS. 30 through 32, thereare shown posterior perspective views of a portion of a vertebral columnundergoing the method of the present invention using a directing sheathaccording to the present invention, showing the bone screws placedthrough the openings of the directing sheath. As can be seen in FIG. 30,the directing sheath 180 is positioned adjacent the vertebral column 196according to the present invention. Next as can be seen in FIG. 31,guidewires 198 are used to place bone screws 208 through openings 188 inthe directing sheath 180. Finally, as can be seem in FIG. 32, thedirecting sheath 180 is removed by the directing sheath 180 into twoseparate halves.

[0185] In one embodiment, there is provided a kit for performing methodsof the present invention. The kit comprises a plurality of bone screwsaccording to the present invention. The kit can also comprise othercomponents of the system of the present invention, such as a guidewiredirecting device, an inflatable connection rod, the curable medium to beinjected and a directing sheath. The curable medium may comprise onepart or it may comprise two or more parts that are mixed before, duringor after injection. In another preferred embodiment, the kit alsocomprises a screwdriver according to the present invention. A controlwith electronic driving circuitry can also be provided, for thermalacceleration of the hardenable media.

[0186] Referring to FIG. 29, a first inflatable connection rod 222 a anda second inflatable connection rod 222 b are illustrated as extendinggenerally in parallel with each other, and also generally in parallel tothe longitudinal axis of the spine. Deviations from this illustratedparallel relationship may also occur, in either or both of the lateralplane as well as the anterior/posterior plane. Such deviations fromparallel may be a consequence of anatomical variations, or proceduralchoices or irregularities as will be appreciated by those of skill inthe art. In any of these configurations, additional stability may beachieved by cross-linking the first inflatable connection rod 222 a withthe second inflatable connection rod 222 b. Thus, in accordance with afurther aspect of the present invention, there is provided a method andapparatus for cross-linking two or more inflatable connection rods.

[0187] Cross-linking may be accomplished in any of a variety ofconfigurations, as will be apparent to those of skill in the art in viewof the disclosure herein. For example, a pair of laterally opposingpedicle screws 208 may be connected to each other by an inflatablecrossbar or solid crossbar as will be apparent from the disclosureherein. Alternatively, the body of the two opposing inflatableconnection rods 222 a and 222 b can also be connected by a crossbar.Although the present discussion will focus primarily upon the latterconstruction, it is to be understood that the present inventioncontemplates any cross connection between a left and right connectionrod, preferably through a procedure in which each of the connection rodsor crossbars is installed in a less invasive or minimally invasiveprocedure.

[0188] Referring to FIG. 33, a side elevational view of a portion of thespine is illustrated. A first and second pedicle screws 208 have beenpositioned in accordance with procedures discussed previously herein. Ahollow needle 214 is illustrated, for guiding a “rocketwire” orguidewire 216 through the coaxial apertures in the first and secondpedicle screws 208.

[0189]FIG. 33 additionally illustrates a cross tic deployment system230, partway through a deployment procedure. The cross tie deploymentsystem 230 comprises an access sheath 232. Access sheath 232 comprisesan elongate tubular body having a proximal end and a distal end, and acentral lumen extending therethrough. In general, the central lumen willhave a diameter within the range of from about 24 French to about 30French, although other diameters may be utilized depending upon the sizeof the device to be deployed. The access sheath 232 is positionedthrough tissue along an axis which intersects the path of the guidewire216, as is advanced from a first pedicle screw 208 through an aperturein a second pedicle screw 208, as illustrated.

[0190] A cross tie support 248 is axially movably positioned within theaccess sheath 232. Cross tie support 248 is connected at a distal end249 through a releasable connector 246 to a cross tie 234. Cross tie 234facilitates connection of a crossbar with a primary inflatableconnection rod, to achieve cross linking of the orthopedic fixationsystem.

[0191] Although a variety of structures for cross tie 234 can beutilized, one convenient construction is illustrated in FIG. 37. Ingeneral, the cross tie 234 includes a first connector 236 such as afirst aperture 238 for receiving an inflatable connection rod 222 as hasbeen discussed previously herein. In one implementation, the aperture238 has an inside diameter of approximately 6 mm. However, diameters ofthe first aperture 238 may be varied widely, depending upon the diameterof the inflatable connection rod 222, and the desired physicalperformance characteristics.

[0192] The cross tie 234 additionally comprises a second connector 240,such as a second aperture 242. The second aperture 242 is adapted toreceive a crossbar 222 c, as illustrated in FIGS. 35 and 36. In theillustrated cross tie 234, a longitudinal axis extending through thefirst aperture 238 is generally perpendicular to a longitudinal axisextending through a second aperture 242, and offset by a spacingdistance which will determine the anterior-posterior spacing between theaxis of an inflatable connection rod 222 a and a corresponding crossbar222 c. In one embodiment, the overall as mounted anterior-posteriorlength of the cross tie 234 is approximately 16 mm, and the width of thecross tie 234 is no more than about 8 mm.

[0193] The cross tie 234 is held in place during the procedure by across tie support 248 through a releasable connector 246. The releasableconnector 246 facilitates the positioning of the cross tie 234 duringthe deployment step, but enables decoupling following proper positioningof at least an inflatable connection rod 222 a and possibly also thecrossbar 222 c. Any of a variety of releasable connection structures maybe utilized, such as a threaded distal end on the cross tie support 248,which threadably engages an aperture on the cross tie 234.

[0194] As illustrated in FIGS. 33, 36 and 37, the cross tie 234 is heldin position by the cross tie support 248 such that the longitudinal axisextending through the first aperture 238 is collinear with the path ofthe guidewire 216. The longitudinal axis of the second aperture 242extends transversely such that it aligns with a second aperture 242 in asecond cross tie 234 to accomplish the cross-linked constructionillustrated in FIGS. 35 and 36.

[0195] Referring to FIG. 34, the first inflatable connection rod 222 ais illustrated as inflated after having been positioned through thefirst aperture 238 on the cross tie 234, as well as through theapproximately collinear apertures on a pair of bone screws 208. This isaccomplished by advancing the guidewire 216 through the first bonescrew, then the first aperture 238 and then the second bone screw 208,as illustrated in progress in FIG. 33. The connection rod 222 a may thenbe advanced over the wire and inflated following the inflatableconnection rod implantation procedures discussed previously herein.

[0196] Preferably, the first aperture 238 is dimensioned with respect tothe connection rod 222 a such that a secure fit is provided between theinflatable connection rod 222 a and cross tie 234 following completecuring of the curable media. If shrinkage of the curable media iscontemplated, the first aperture 238 may be defined within an annularring on the frame 244 which has an expansion break extendingtherethrough. In this manner, inflation of the inflatable connection rod222 a can be accomplished such that the expansion break allows a slightenlargement of the diameter of the first aperture 238. Upon transverseshrinkage of the inflatable connection rod 222 a during the curingprocess, the natural bias imparted by the frame 244 allows the firstaperture 238 to shrink, thereby retaining a tight fit with theinflatable connection rod 222 a throughout a range of diameters. Thisconstruction may also be applied to the apertures extending through thebone screws 208, as well as the second apertures 242.

[0197] The cross tie support 248 is illustrated in FIG. 34 as detachedfrom the cross tie 234, such as by unscrewing the releasable connector246. This may be accomplished before or after positioning of thecrossbar 222 c, depending upon the clinical judgment of thepractitioner.

[0198] The final construction is illustrated in FIG. 35. As seentherein, a crossbar 222 c extends between a first cross tie 234 carriedby the first inflatable connection rod 222 a and a second cross tie 234carried by the second inflatable connection rod 222 b. The crossbar 222c may be positioned through the pair of opposing apertures 242 using thesame techniques discussed and illustrated previously herein for theimplantation of the inflatable connection rods 222. The initial positionof a curved needle and guidewire for positioning the crossbar 222 c isschematically illustrated in FIG. 36.

[0199] Although only a single crossbar 222 c is illustrated, two orthree or four or more crossbars 222 c may alternatively be used,depending upon the axial lengths of the inflatable connection rods 222 aand 222 b, and the desired structural integrity of the finishedassembly. In addition, although the crossbar 222 c is illustrated asextending generally perpendicular to the longitudinal axis of each ofthe inflatable connection rods 222 a and 222 b, the crossbar 222 c maycross each of the inflatable connection rods 222 at any of a variety ofangles ranging from approximately +45° to −45° with respect to theillustrated position. Thus, the crossbar 222 c may be implanted at adiagonal if the desired structural integrity can be thus achieved.

[0200] The crossbar 222 c may comprise any of a variety of forms. Forexample, the crossbar illustrated in FIG. 35 may be identical inconstruction to any of the inflatable connection rods discussedpreviously herein.

[0201] In an alternate application of the cross-linking technology ofthe present invention, the crossbar is constructed in a manner whichenables elimination of the separate cross tie 234. Referring to FIGS.40-43, the crossbar comprises a first portal 250, for receiving a firstinflatable connection rod 222 a, and a second portal 252 for receiving asecond inflatable connection rod 222 b. First portal 250 and secondportal 252 are spaced apart by an elongate tubular body 254. Body 254may be a solid element, such as a polymeric extrusion, molded part ormetal rod. Alternatively, body 254 comprises a tubular sleeve, such asillustrated in FIGS. 40-42. In the illustrated embodiment, the tubularsleeve is provided with a plurality of circumferentially extending slots254, to permit flexibility of the crossbar. 222 c during deployment.Slots 254 may be formed such as by laser cutting a stainless steel,nickel-titanium alloy or other tube.

[0202]FIG. 41 schematically illustrates the distal end of a deploymentsystem 258 for deploying the crossbar 222 c of FIG. 40. The tubular body254 is carried by a dilator 260 which extends axially therethrough. Inone application, the dilator 260 is approximately 21 French, foraccommodating a tubular body 254 having an inside diameter of about 7 mmand an outside diameter of about 8 mm.

[0203] The 21 French dilator 260 is advanced over a stiff 0.038″guidewire, with an 8 French catheter. A 24 French pusher sheath 262 ispositioned proximally of the tubular body 254.

[0204] Using this deployment system, the tubular body 254 may bepositioned relative to two pairs of bone screws 208 as illustratedschematically in FIG. 42. A first pair of bone screws 208 a and 208 bcontain apertures which coaxially align with the first portal 250. Asecond pair of bone screws 208 c and 208 d carry apertures which arecoaxially aligned with a second portal 252. Once positioned asillustrated in FIG. 242, a guiding assembly such as a curved needle 214and a rocket wire 216 may be advanced as illustrated in FIG. 42. Aninflatable connection rod 222 a may thereafter be advanced along thewire, and inflated to secure the first and second bone screws 208 a and208 b, and also the crossbar 222 c. A similar procedure may beaccomplished to install a second inflatable connection rod 222 b.

[0205] The tubular body 254 may by itself provide sufficientcross-linking strength for the intended purpose. Alternatively, thetubular body 254 may be filled with a curable media 266 to enhance thestructural integrity of the resulting assembly. For example, asillustrated in FIG. 43, the deployment system 258 may additionallycomprise an inflatable container such as an inflatable connection rodpreviously disclosed herein, in communication with a source of curablemedia through an inflation lumen. Depending upon the construction of theinflatable container, it may be filled with a hardenable media 266either prior to or following positioning of the first inflatableconnection rod 222 a and second inflatable rod 222 b as discussedpreviously herein.

[0206] The embodiment of FIGS. 40-43 is illustrated in position withinthe patient, in FIGS. 38 and 39. As can be seen from FIGS. 38 and 39,the crossbar 222 c resides within the plane that extends through theapertures in the bone screws 208. Thus, the crossbar 222 c in theconfiguration illustrated in FIGS. 38 and 39 is lower profile, orpositioned anteriorly of the crossbar 222 c in the embodiment of FIGS.34 and 35. The location of the crossbar 222 c in FIGS. 38 and 39 is not,however, precisely to scale or in the exact or only implantable locationin the spine. For example, the crossbar 222 c may extend laterallythrough a space in-between an adjacent pair of caudal and cephaladspinous processes. If the crossbar 222 c is preferably positioned at amore caudal or cephalad position than the opening between adjacentspinous processes, or if the crossbar 222 c is preferably positionedfarther anteriorly than would be permitted by the transverse process orother bony structure, the crossbar 222 c may extend through an aperturebored through the bone, or portions of the bone may be removed. Any of avariety of bores or drills may be utilized to bore a transverseaperture, such as through a spinous process. The crossbar 222 c maythereafter be advanced through the bore and locked into place using thefirst and second support structure 222 a and 222 b as is disclosedelsewhere herein.

[0207] The various materials, methods and techniques described aboveprovide a number of ways to carry out the invention. Of course, it is tobe understood that not necessarily all objectives or advantagesdescribed may be achieved in accordance with any particular embodimentdescribed herein. Thus, for example, those skilled in the art willrecognize that the materials such as media may be made and the methodsmay be performed in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otherobjectives or advantages as may be taught or suggested herein.

[0208] Although the present invention has been described in terms ofcertain preferred embodiments, other embodiments of the inventionincluding variations in dimensions, configuration and materials will beapparent to those of skill in the art in view of the disclosure herein.In addition, all features discussed in connection with any oneembodiment herein can be readily adapted for use in other embodimentsherein. The use of different terms or reference numerals for similarfeatures in different embodiments does not imply differences other thanthose which may be expressly set forth. Accordingly, the presentinvention is intended to be described solely by reference to theappended claims, and not limited to the preferred embodiments disclosedherein.

What is claimed is:
 1. A formed in place orthopedic device, comprising:an outer wall, defining a cavity therein; and a hardenable media withinthe cavity to form the orthopedic device, said hardenable mediacomprising a resin and hardener mixture that is substantially cured at atemperature below about 45° C. in about 90 minutes or less; wherein thehardenable media is hardened while the device is positioned within thebody of a patient to create the formed in place orthopedic device. 2.The formed in place orthopedic device of claim 1, wherein saidhardenable media comprises an epoxy resin.
 3. The formed in placeorthopedic device of claim 2, wherein said epoxy resin comprises a totalof about 65-75% by weight of one or more diepoxide resins and a total ofabout 25-35% by weight of one or more amine curing agents.
 4. The formedin place orthopedic device of claim 2, wherein said epoxy resincomprises about 45-52% by weight aromatic diepoxide resin, about 19-23%by weight aliphatic diepoxide resin, about 20-29% by weightdialkylamines and about 4-9% cycloalkylamines.
 5. The formed in placeorthopedic device of claim 4, wherein the aromatic diepoxide resincomprises diglycidyl ether of Bisphenol A or diglycidyl ether ofBisphenol F.
 6. The formed in place orthopedic device of claim 4,wherein the aliphatic diepoxide resin comprises one or more alkane diolsof glycidyl ether.
 7. The formed in place orthopedic device of claim 4,wherein the dialkylamines are according to the formula H₂N—R—NH₂,wherein R is a branched or unbranched C₂-C₁₀ alkyl group.
 8. The formedin place orthopedic device of claim 4, wherein the cycloalkylamines areN-aminoalkylpiperazines.
 9. The formed in place orthopedic device ofclaim 4, wherein the aromatic diepoxide resin comprises diglycidyl etherof Bisphenol A, the aliphatic diepoxide resin comprises butane diol ofglycidyl ether, the dialkylamine comprises 1,3-diaminopropane, and thecycloalkylamine comprises N-aminoethylpiperazine.
 10. The formed inplace orthopedic device of claim 1, wherein said hardenable media curesto a hardened form having a static compression bending value (ASTMF1717) of at least 100 lbs.
 11. A bone fixation device, comprising: adelivery catheter; comprising an inflatable member; a hardenable mediacontained within the inflatable member, said hardenable media comprisingan epoxy that cures to a hardened form having a static compressionbending value (ASTM F1717) of at least 90 lbs in about 90 minutes orless; and at least two anchors having portals, wherein said inflatablemember extends through said portals of said at least two anchors. 12.The bone fixation device of claim 11, wherein said epoxy resin comprisesabout 45-52% by weight aromatic diepoxide resin, about 19-23% by weightaliphatic diepoxide resin, about 20-29% by weight dialkylamines andabout 4-9% cycloalkylamines.
 13. The bone fixation device of claim 12,wherein the aromatic diepoxide resin comprises diglycidyl ether ofBisphenol A or diglycidyl ether of Bisphenol F.
 14. The bone fixationdevice of claim 14, wherein the aliphatic diepoxide resin comprises oneor more alkane diols of glycidyl ether.
 15. The bone fixation device ofclaim 13, wherein the dialkylamines are according to the formulaH₂N—R—NH₂, wherein R is a branched or unbranched C₂-C₁₀ alkyl group. 16.The bone fixation device of claim 15, wherein the cycloalkylamines areN-aminoalkylpiperazines.
 17. The bone fixation device of claim 12,wherein the aromatic diepoxide resin comprises diglycidyl ether ofBisphenol A, the aliphatic diepoxide resin comprises butane diol ofglycidyl ether, the dialkylamine comprises 1,3-diaminopropane, and thecycloalkylamine comprises N-aminoethylpiperazine.
 18. The bone fixationdevice of claim 11, wherein the hardenable media cures at temperaturebelow about 45° C.
 19. The bone fixation device of claim 11, wherein thehardenable media has a static compression bending value (ASTM F1717) ofat least 150 lbs within 12 hours.
 20. An orthopedic fixation device,comprising: an elongate, flexible tubular body having a distal end and aproximal end, said body forming a central lumen; a manifold at theproximal end of the tubular body comprising at least one port; aninflatable member having a proximal end, a distal end, and an interior,removably attached to the distal end of the tubular body; a hardenablemedia for inflating said inflatable member, said hardenable mediacomprising about 45-52% by weight aromatic diepoxide resin, about 19-23%by weight aliphatic diepoxide resin, about 20-29% by weightdialkylamines and about 4-9% cycloalkylamines; and a valve, provided atthe proximal end of the inflatable member.
 21. The orthopedic fixationdevice of claim 20, wherein the aromatic diepoxide resin comprisesdiglycidyl ether of Bisphenol A or diglycidyl ether of Bisphenol F; thealiphatic diepoxide resin comprises one or more alkane diols of glycidylether; the cycloalkylamines are N-aminoalkylpiperazines; and thedialkylamines are according to the formula H₂N—R—NH₂, wherein R is abranched or unbranched C₂-C₁₀ alkyl group.
 22. The orthopedic fixationdevice of claim 21, wherein the aromatic diepoxide resin comprisesdiglycidyl ether of Bisphenol A, the aliphatic diepoxide resin comprisesbutane diol of glycidyl ether, the dialkylamine comprises1,3-diaminopropane, and the cycloalkylamine comprisesN-aminoethylpiperazine.
 23. The orthopedic fixation device of claim 20,wherein said hardenable media, when cured, has a static compressionbending value of at least 100 lbs (ASTM F1717).
 24. The orthopedicfixation device of claim 20, wherein the media is substantially cured inabout 90 minutes or less.
 25. The orthopedic fixation device of claim20, wherein the media cures at a temperature of about 45° C. or less.26. A method of forming an orthopedic device at a treatment site withinthe body of a patient, comprising the steps of: positioning an outerwall at the treatment site within the patient, the outer wall defining achamber therein; and introducing a hardenable media into the chamber,wherein the hardenable media cures from a liquid form to a hardened formhaving a static compression bending value of at least 90 lbs (ASTMF1717) in about 90 minutes or less.
 27. A method of forming anorthopedic device as in claim 26, wherein the positioning step comprisespositioning the outer wall between two bone anchors.
 28. The method ofclaim 26, wherein said hardenable media comprises about 45-52% by weightaromatic diepoxide resin, about 19-23% by weight aliphatic diepoxideresin, about 20-29% by weight dialkylamines and about 4-9%cycloalkylamines.
 29. The method of claim 28, wherein the aromaticdiepoxide resin comprises diglycidyl ether of Bisphenol A or diglycidylether of Bisphenol F; the aliphatic diepoxide resin comprises one ormore alkane diols of glycidyl ether; the cycloalkylamines areN-aminoalkylpiperazines; and the dialkylamines are according to theformula H₂N—R—NH₂, wherein R is a branched or unbranched C₂-C₁₀ alkylgroup.
 30. The method of claim 28, wherein the aromatic diepoxide resincomprises diglycidyl ether of Bisphenol A, the aliphatic diepoxide resincomprises butane diol of glycidyl ether, the dialkylamine comprises1,3-diaminopropane, and the cycloalkylamine comprisesN-aminoethylpiperazine.
 31. The method of claim 26, wherein thehardenable media cures at temperature below about 45° C.
 32. The methodof claim 26, wherein the hardenable media has a static compressionbending value (ASTM F1717) of at least 150 lbs within 12 hours.
 33. Amethod of stabilizing an orthopedic fracture, comprising: inserting atleast two anchors having portals into a bone; delivering an orthopedicdevice comprising an inflatable balloon to the bone; and inflating saidballoon with a hardenable media comprising about 45-52% by weightaromatic diepoxide resin, about 19-23% by weight aliphatic diepoxideresin, about 20-29% by weight dialkylamines and about 4-9%cycloalkylamines; wherein said orthopedic device extends through saidportals, such that said inflating fixes said anchors in relation to oneanother.
 34. The method of claim 33, wherein the aromatic diepoxideresin comprises diglycidyl ether of Bisphenol A or diglycidyl ether ofBisphenol F; the aliphatic diepoxide resin comprises one or more alkanediols of glycidyl ether; the cycloalkylamines areN-aminoalkylpiperazines; and the dialkylamines are according to theformula H₂N—R—NH₂, wherein R is a branched or unbranched C₂-C₁₀ alkylgroup.
 35. The method of claim 33, wherein the aromatic diepoxide resincomprises diglycidyl ether of Bisphenol A, the aliphatic diepoxide resincomprises butane diol of glycidyl ether, the dialkylamine comprises1,3-diaminopropane, and the cycloalkylamine comprisesN-aminoethylpiperazine.
 36. The method of claim 33, wherein saidhardenable media, when cured, has a static compression bending value ofat least 100 lbs. (ASTM F1717).
 37. The method of claim 33, wherein themedia is substantially cured in about 90 minutes or less.
 38. The methodof claim 33, wherein the media cures at a temperature of about 45° C. orless.
 39. A method of stabilizing an orthopedic fracture, comprising:inserting at least two anchors having portals into a bone; delivering anorthopedic device comprising an inflatable balloon through the portals;and inflating said balloon with a liquid curable material; wherein theinflating step fixes said anchors in relation to one another and thecurable material is substantially cured at a temperature below about 45°C. in about 90 minutes or less.
 40. The method of claim 39, wherein saidcurable material comprises about 45-52% by weight aromatic diepoxideresin, about 19-23% by weight aliphatic diepoxide resin, about 20-29% byweight dialkylamines and about 4-9% cycloalkylamines.
 41. The method ofclaim 40, wherein the aromatic diepoxide resin comprises diglycidylether of Bisphenol A or diglycidyl ether of Bisphenol F; the aliphaticdiepoxide resin comprises one or more alkane diols of glycidyl ether;the cycloalkylamines are N-aminoalkylpiperazines; and the dialkylaminesare according to the formula H₂N—R—NH₂, wherein R is a branched orunbranched C₂-C₁₀ alkyl group.
 42. The method of claim 40, wherein thearomatic diepoxide resin comprises diglycidyl ether of Bisphenol A, thealiphatic diepoxide resin comprises butane diol of glycidyl ether, thedialkylamine comprises 1,3-diaminopropane, and the cycloalkylaminecomprises N-aminoethylpiperazine.
 43. The method of claim 39, whereinsaid hardenable media, when cured, has a static compression bendingvalue of at least 100 lbs. (ASTM F1717).
 44. A formed in place medicaldevice, comprising: an outer wall, defining a cavity therein; and ahardenable media within the cavity to form the medical device, saidhardenable media comprising a resin and hardener mixture that cures at atemperature below about 45° C. wherein said cured media has a staticcompression bending value (ASTM F1717) of at least 150 lbs; wherein thehardenable media is hardened while the device is positioned within thebody of a patient to create the formed in place medical device.